Chapter 45

Ir*reg"u*late (?), v. t. To make irregular; to disorder. [Obs.] Sir T. Browne.

Ir*reg"u*lous (?), a. Lawless. [Obs.] Shak.

Ir`re*ject"a*ble (?), a. That can not be rejected; irresistible. Boyle.

Ir`re*laps"a*ble (?), a. Not liable to relapse; secure. Dr. H. More.

Ir`re*late (?), a. Irrelative; unconnected.

Ir`re*la"tion (?), n. The quality or state of being irrelative; want of connection or relation.

Ir*rel"a*tive (?), a. Not relative; without mutual relations; unconnected. -- Ir*rel"a*tive*ly, adv.

Irrelative chords (Mus.), those having no common tone. -- Irrelative repetition (Biol.), the multiplication of parts that serve for a common purpose, but have no mutual dependence or connection. Owen.

Ir*rel"a*vance (?), n. Irrelevancy.

Ir*rel"a*van*cy (?), n. The quality or state of being irrelevant; as, the irrelevancy of an argument.

Ir*rel"a*vant (?), a. Not relevant; not applicable or pertinent; not bearing upon or serving to support; foreign; extraneous; as, testimony or arguments irrelevant to a case. -- Ir*rel"a*vant*ly, adv.

Ir`re*liev"a*ble (?), a. Not admitting relief; incurable; hopeless.

Ir`re*li"gion (?), n. [L. irreligio: cf. F. irréligion. See In- not, and Religion.] The state of being irreligious; want of religion; impiety.

Ir`re*li"gion*ist, n. One who is irreligious.

Ir`re*li"gious (?), a. [L. irreligiosus: cf. F. irréligieux.]

1. Destitute of religion; not controlled by religious motives or principles; ungodly. Cf. Impious.

Shame and reproach are generally the portion of the impious and irreligious.

South.

2. Indicating a want of religion; profane; wicked; as, irreligious speech.

Ir`re*li"gious*ly, adv. In an irreligious manner.

Ir`re*li"gious*ness, n. The state or quality of being irreligious; ungodliness.

Ir*re"me*a*ble (?), a. [L. irremeabilis; pref. ir- not + remeabilis returning, fr. remeare: cf. F. irréméable. See Remeant.] Admitting no return; as, an irremeable way. [Obs.] Dryden.

Ir`re*me"di*a*ble (?), a. [L. irremediabilis: cf. F. irrémédiable. See In- not, and Remediable.] Not to be remedied, corrected, or redressed; incurable; as, an irremediable disease or evil.

Ir`re*me"di*a*ble*ness, n. The state or quality of being irremediable.

Ir`re*me"di*a*bly, adv. In a manner, or to a degree, that precludes remedy, cure, or correction.

Ir`re*mis"si*ble (?), a. [L. irremissibilis: cf. F. irrémissible. See In- not, and Remissible.] Not remissible; unpardonable; as, irremissible crimes. Burke. -- Ir`re*mis"si*ble, n. -- Ir`re*mis"si*bly, adv.

Ir`re*mis"sion (?), n. Refusal of pardon.

Ir`re*mis"sive (?), a. Not remitting; unforgiving.

Ir`re*mit"ta*ble (?), a. Not capable of being remitted; irremissible. Holinshed.

Ir`re*mov`a*bil"i*ty (?), n. The quality or state of being irremovable; immovableness.

Ir`re*mov"a*ble (?), a. Not removable; immovable; inflexible. Shak. -- Ir`re*mov"a*bly, adv.

Ir`re*mov"al (?), n. Absence of removal.

Ir`re*mu"ner*a*ble (?), a. [L. irremunerabilis: cf. F. irrémunérable. See Remunerate.] Not remunerable; not capable of remuneration.

Ir`re*nowned" (?), a. Not renowned. [Obs.]

Ir*rep`a*ra*bil"i*ty (?), n. [Cf. F. irréparabilité.] The quality or state of being irreparable; irreparableness. Sterne.

Ir*rep"a*ra*ble (?), a. [L. irreparabilis: cf. F. irréparable. See In- not, and Reparable.] Not reparable; not capable of being repaired, recovered, regained, or remedied; irretrievable; irremediable; as, an irreparable breach; an irreparable loss. Shak.

Ir*rep"a*ra*ble*ness, n. Quality of being irreparable.

Ir*rep"a*ra*bly, adv. In an irreparable manner.

Ir`re*peal`a*bil"i*ty (?), n. The quality or state of being irrepealable.

Ir`re*peal"a*ble (?), a. Not repealable; not capable of being repealed or revoked, as a law. -- Ir`re*peal"a*ble*ness, n. -- Ir`re*peal"a*bly, adv.

Ir`re*pent"ance (?), n. Want of repentance; impenitence. Bp. Montagu.

{ Ir`re*plev"i*a*ble (?), Ir`re*plev"i*sa*ble (?), } a. (Law) Not capable of being replevied.

Ir*rep`re*hen"si*ble (?), a. [L. irreprehensibilis: cf. F. irrépréhensible. See Reprehensible.] Not reprehensible; blameless; innocent. -- Ir*rep`re*hen"si*ble*ness, n. -- Ir*rep`re*hen"si*bly, adv.

Ir*rep`re*sent"a*ble (?), a. Not capable of being represented or portrayed.

Ir`re*press"i*ble (?), a. Not capable of being repressed, restrained, or controlled; as, irrepressible joy; an irrepressible conflict. W. H. Steward.

Ir`re*press"i*bly, adv. In a manner or to a degree that can not be repressed.

Ir`re*proach"a*ble (?), a. [Pref. ir- not + reproachable: cf. F. irréprochable.] Not reproachable; above reproach; not deserving reproach; blameless.

He [Berkely] erred, -- and who is free from error? -- but his intentions were irreproachable.

Beattie.

Ir`re*proach"a*ble*ness, n. The quality or state of being irreproachable; integrity; innocence.

Ir`re*proach"a*bly, adv. In an irreproachable manner; blamelessly.

Ir`re*prov"a*ble (?), a. Incapable of being justly reproved; irreproachable; blameless; upright. - - Ir`re*prov"a*ble*ness, n. -- Ir`re*prov"a*bly, adv.

Ir`rep*ti"tious (?), a. [L. irrepere, irreptum, to creep in; pref. ir- in + repere to creep.] Surreptitious; spurious. [Obs.] Dr. Castell (1673).

Ir*rep"u*ta*ble (?), a. Disreputable. [Obs.]

Ir`re*sil"i*ent (?), a. Not resilient; not recoiling or rebounding; inelastic.

Ir`re*sist"ance (?), n. Nonresistance; passive submission.

Ir`re*sist`i*bil"i*ty (?), n. [Cf. F. irrésistibilité.] The quality or state of being irresistible, irresistibleness.

Ir`re*sist"i*ble (?), a. [Pref. ir- not + resistible: cf. F. irrésistible.] That can not be successfully resisted or opposed; superior to opposition; resistless; overpowering; as, an irresistible attraction.

An irresistible law of our nature impels us to seek happiness.

J. M. Mason.

Ir`re*sist"i*ble*ness, n. Quality of being irresistible.

Ir`re*sist"i*bly, adv. In an irresistible manner.

Ir`re*sist"less, a. Irresistible. [Obs.] Glanvill.

Ir*res"o*lu*ble (?), a. [L. irresolubilis: cf. F. irrésoluble. See Resoluble, and cf. Irresolvable.]

1. Incapable of being dissolved or resolved into parts; insoluble. Boyle.

2. Incapable of being relieved or assisted. [Obs.]

The second is in the irresoluble condition of our souls after a known sin committed.

Bp. Hall.

Ir*res"o*lu*ble*ness, n. The state or quality of being irresoluble; insolubility.

Ir*res"o*lute (?), a. [Pref. ir- not + resolute: cf. F. irrésolu, L. irresolutus not loosened.] Not resolute; not decided or determined; wavering; given to doubt or irresolution.

Weak and irresolute is man.

Cowper.

Syn. -- Wavering; vacillating; undetermined; undecided; unsettled; fickle; changeable; inconstant.

-- Ir*res"o*lute*ly, adv. -- Ir*res"o*lute*ness, n.

Ir*res`o*lu"tion (?), n. [Cf. F. irrésolution.] Want of resolution; want of decision in purpose; a fluctuation of mind, as in doubt, or between hope and fear; irresoluteness; indecision; vacillation.

Irresolution on the schemes of life which offer themselves to our choice, and inconstancy in pursuing them, are the greatest causes of all unhappiness.

Addison.

Ir`re*solv`a*bil"i*ty (?), n. The quality of being irresolvable; irresolvableness.

Ir`re*solv"a*ble (?), a. [Pref. ir- not + resolvable. Cf. Irresoluble.] Incapable of being resolved; not separable into component parts.

Irresolvable nebulæ (Astron.), nebulæ of a cloudlike appearance, which have not yet been resolved by the telescope into stars. Sir W. Herschel.

Ir`re*solv"a*ble*ness, n. The quality or state of being irresolvable; irresolvability.

Ir`re*solv"ed*ly, adv. Without settled determination; in a hesitating manner; doubtfully. [R.]

Ir`re*spec"tive (-spk"tv), a. 1. Without regard for conditions, circumstances, or consequences; unbiased; independent; impartial; as, an irrespective judgment.

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According to this doctrine, it must be resolved wholly into the absolute, irrespective will of God.

Rogers.

2. Disrespectful. [Obs.] Sir C. Cornwallis.

Irrespective of, regardless of; without regard to; as, irrespective of differences.

Ir`re*spec"tive*ly (r`r*spk"tv*l), adv. Without regard to conditions; not taking circumstances into consideration.

Prosperity, considered absolutely and irrespectively, is better and more desirable than adversity.

South.

Ir*res"pi*ra*ble (?), a. [L. irrespirabilis: cf. F. irrespirable. See Respirable.] Unfit for respiration; not having the qualities necessary to support animal life; as, irrespirable air.

Ir`re*spon`si*bil"i*ty (?), n. [Cf. F. irresponsabilité.] Want of, or freedom from, responsibility or accountability.

Ir`re*spon"si*ble (?), a. [Pref. ir- not + responsible: cf. F. irresponsable.]

1. Nor responsible; not liable or able to answer for consequences; innocent.

2. Not to be trusted; unreliable.

Ir`re*spon"si*bly, adv. So as not to be responsible.

Ir`re*spon"sive (?), a. Not responsive; not able, ready, or inclined to respond.

Ir`re*sus"ci*ta*ble (?), a. Incapable of being resuscitated or revived. -- Ir`re*sus"ci*ta*bly, adv.

Ir`re*ten"tion (?), n. Want of retaining power; forgetfulness. De Quincey.

Ir`re*ten"tive (?), a. Not retentive; as, an irretentive memory.

Ir`re*trace"a*ble (?), a. Incapable of being retraced; not retraceable.

Ir`re*tract"ile (?), a. 1. Not retractile.

2. Not tractile or ductile. [R.] Sir W. Hamilton.

Ir`re*triev"a*ble (?), a. Not retrievable; irrecoverable; irreparable; as, an irretrievable loss.

Syn. -- Irremediable; incurable; irrecoverable.

Ir`re*triev"a*ble*ness, n. The state or quality of being irretrievable.

Ir`re*triev"a*bly, adv. In an irretrievable manner.

Ir`re*turn"a*ble (?), a. Not to be returned.

Ir`re*veal"a*ble (?), a. Incapable of being revealed. -- Ir`re*veal"a*bly, adv.

Ir*rev"er*ence (?), n. [L. irreverentia: cf. F. irrévérence.] The state or quality of being irreverent; want of proper reverence; disregard of the authority and character of a superior.

Ir*rev"er*end (?), a. Irreverent. [Obs.]

Immodest speech, or irreverend gesture.

Strype.

Ir*rev"er*ent (?), a. [L. irreverens, -entis: cf. F. irrévérent. See In- not, and Reverent.] Not reverent; showing a want of reverence; expressive of a want of veneration; as, an irreverent babbler; an irreverent jest.

Ir*rev"er*ent*ly, adv. In an irreverent manner.

Ir`re*vers`i*bil"i*ty (?), n. The state or quality of being irreversible; irreversibleness.

Ir`re*vers"i*ble (?), a. 1. Incapable of being reversed or turned about or back; incapable of being made to run backward; as, an irreversible engine.

2. Incapable of being reversed, recalled, repealed, or annulled; as, an irreversible sentence or decree.

This rejection of the Jews, as it is not universal, so neither is it final and irreversible.

Jortin.

Syn. -- Irrevocable; irrepealable; unchangeable.

Ir`re*vers"i*ble*ness (?), n. The state or quality of being irreversible.

Ir`re*vers"i*bly, adv. In an irreversible manner.

Ir*rev`o*ca*bil"i*ty (?), n. [Cf. F. irrévocabilité.] The state or quality of being irrevocable; irrevocableness.

Ir*rev"o*ca*ble (?), a. [L. irrevocabilis: cf. F. irrévocable. See In- not, and Revoke, and cf. Irrevocable.] Incapable of being recalled or revoked; unchangeable; irreversible; unalterable; as, an irrevocable promise or decree; irrevocable fate.

Firm and irrevocable is my doom.

Shak.

-- Ir*rev"o*ca*ble*ness, n. -- Ir*rev"o*ca*bly, adv.

Ir`re*vok"a*ble (?), a. [Pref. ir- not + revoke.] Irrevocable. [R.]

Ir*rev"o*lu*ble (?), a. That has no finite period of revolution; not revolving. [R.]

The dateless and irrevoluble circle of eternity.

Milton.

Ir`rhe*tor"ic*al (?), a. Not rhetorical.

Ir"ri*gate (?), v. t. [imp. & p. p. Irrigated (?); p. pr. & vb. n. Irrigating (?).] [L. irrigatus, p. p. of irrigare to irrigate: ir- in + rigare to water; prob. akin to E. rain. See Rain.]

1. To water; to wet; to moisten with running or dropping water; to bedew.

2. (Agric.) To water, as land, by causing a stream to flow upon, over, or through it, as in artificial channels.

Ir`ri*ga"tion (?), n. [L. irrigatio: cf. F. irrigation.] The act or process of irrigating, or the state of being irrigated; especially, the operation of causing water to flow over lands, for nourishing plants.

Ir*rig"u*ous (?), a. [L. irriguus. See Irrigate.]

1. Watered; watery; moist; dewy. [Obs.]

The flowery lap Of some irriguous valley spreads her store.

Milton.

2. Gently penetrating or pervading. [Obs.] J. Philips.

Ir*ris"i*ble (?), a. [Pref. ir- not + risible. See Irrision.] Not risible. [R.]

Ir*ri"sion (?), n. [L. irrisio, fr. irridere, irrisum, to laugh at; pref. ir- in + ridere to laugh: cf. F. irrision.] The act of laughing at another; derision.

This being spoken scepticè, or by way of irrision.

Chapman.

Ir`ri*ta*bil"i*ty (?), n. [L. irritabilitas: cf. F. irritabilité.]

1. The state or quality of being irritable; quick excitability; petulance; fretfulness; as, irritability of temper.

2. (Physiol.) A natural susceptibility, characteristic of all living organisms, tissues, and cells, to the influence of certain stimuli, response being manifested in a variety of ways, -- as that quality in plants by which they exhibit motion under suitable stimulation; esp., the property which living muscle possesses, of responding either to a direct stimulus of its substance, or to the stimulating influence of its nerve fibers, the response being indicated by a change of form, or contraction; contractility.

3. (Med.) A condition of morbid excitability of an organ or part of the body; undue susceptibility to the influence of stimuli. See Irritation, n., 3.

Ir"ri*ta*ble (?), a. [L. irritabilis: cf. F. irritable. See Irritate.]

1. Capable of being irritated.

2. Very susceptible of anger or passion; easily inflamed or exasperated; as, an irritable temper.

Vicious, old, and irritable.

Tennyson.

3. (Physiol.) Endowed with irritability; susceptible of irritation; capable of being excited to action by the application of certain stimuli.

4. (Med.) Susceptible of irritation; unduly sensitive to irritants or stimuli. See Irritation, n., 3.

Syn. -- Excitable; irascible; touchy; fretful; peevish.

Ir"ri*ta*ble*ness, n. Irritability.

Ir"ri*ta*bly, adv. In an irritable manner.

Ir"ri*tan*cy (?), n. [From 1st Irritant.] (Scots Law) The state or quality of being null and void; invalidity; forfeiture. Burrill.

Ir"ri*tan*cy, n. [From 2d Irritant.] The state or quality of being irritant or irritating.

Ir"ri*tant (?), a. [LL. irritants, -antis, p. pr. of irritare to make null, fr. L. irritus void; pref. ir- not + ratus established.] (Scots Law) Rendering null and void; conditionally invalidating.

The states elected Harry, Duke of Anjou, for their king, with this clause irritant; that, if he did violate any part of his oath, the people should owe him no allegiance.

Hayward.

Ir"ri*tant, a. [L. irritans, -antis, p. pr. of irritare: cf. F. irritant. See Irritate to excite.] Irritating; producing irritation or inflammation.

Ir"ri*tant, n. [Cf. F. irritant.]

1. That which irritates or excites.

2. (Physiol. & Med.) Any agent by which irritation is produced; as, a chemical irritant; a mechanical or electrical irritant.

3. (Toxicology) A poison that produces inflammation.

Counter irritant. See under Counter. -- Pure irritant (Toxicology), a poison that produces inflammation without any corrosive action upon the tissues.

Ir"ri*tate (?), v. t. [See 1 st Irritant.] To render null and void. [R.] Abp. Bramhall.

Ir"ri*tate, v. t. [imp. & p. p. Irritated (?); p. pr. & vb. n. Irritating (?).] [L. irritatus, p. p. of irritare. Of doubtful origin.]

1. To increase the action or violence of; to heighten excitement in; to intensify; to stimulate.

Cold maketh the spirits vigorous and irritateth them.

Bacon.

2. To excite anger or displeasure in; to provoke; to tease; to exasperate; to annoy; to vex; as, the insolence of a tyrant irritates his subjects.

Dismiss the man, nor irritate the god: Prevent the rage of him who reigns above.

Pope.

3. (Physiol.) To produce irritation in; to stimulate; to cause to contract. See Irritation, n., 2.

4. (Med.) To make morbidly excitable, or oversensitive; to fret; as, the skin is irritated by friction; to irritate a wound by a coarse bandage.

Syn. -- To fret; inflame; excite; provoke; tease; vex; exasperate; anger; incense; enrage. -- To Irritate, Provoke, Exasperate. These words express different stages of excited or angry feeling. Irritate denotes an excitement of quick and slightly angry feeling which is only momentary; as, irritated by a hasty remark. To provoke implies the awakening of some open expression of decided anger; as, a provoking insult. Exasperate denotes a provoking of anger at something unendurable. Whatever comes across our feelings irritates; whatever excites anger provokes; whatever raises anger to a high point exasperates. "Susceptible and nervous people are most easily irritated; proud people are quickly provoked; hot and fiery people are soonest exasperated." Crabb.

Ir"ri*tate (?), a. Excited; heightened. [Obs.]

Ir`ri*ta"tion (?), n. [L. irritatio: cf. F. irritation.]

1. The act of irritating, or exciting, or the state of being irritated; excitement; stimulation, usually of an undue and uncomfortable kind; especially, excitement of anger or passion; provocation; annoyance; anger.

The whole body of the arts and sciences composes one vast machinery for the irritation and development of the human intellect.

De Quincey.

2. (Physiol.) The act of exciting, or the condition of being excited to action, by stimulation; -- as, the condition of an organ of sense, when its nerve is affected by some external body; esp., the act of exciting muscle fibers to contraction, by artificial stimulation; as, the irritation of a motor nerve by electricity; also, the condition of a muscle and nerve, under such stimulation.

3. (Med.) A condition of morbid excitability or oversensitiveness of an organ or part of the body; a state in which the application of ordinary stimuli produces pain or excessive or vitiated action.

Ir"ri*ta*tive (?), a. 1. Serving to excite or irritate; irritating; as, an irritative agent.

2. Accompanied with, or produced by, increased action or irritation; as, an irritative fever. E. Darwin.

Ir"ri*ta*to*ry (?), a. Exciting; producing irritation; irritating. [R.] Hales.

Ir"ro*rate (?), v. t. [imp. & p. p. Irrorated (?); p. pr. & vb. n. Irrorating.] [L. irroratus, p. p. of irrorare to bedew; pref. ir- in + ros, roris, dew.] To sprinkle or moisten with dew; to bedew. [Obs.]

Ir"ro*rate (?), a. (Zoöl.) Covered with minute grains, appearing like fine sand.

Ir`ro*ra"tion (?), n. [Cf. F. irroration.] The act of bedewing; the state of being moistened with dew. [Obs.] Chambers.

Ir`ro*ta"tion*al (?), a. (Physics) Not rotatory; passing from one point to another by a movement other than rotation; -- said of the movement of parts of a liquid or yielding mass. Sir W. Thomson.

Ir*ru"bric*al (?), a. Contrary to the rubric; not rubrical.

Ir"ru*gate (?), v. t. [L. irrugatus, p. p. of irrugare to wrinkle.] To wrinkle. [Obs.]

Ir*rupt"ed (?), a. [L. irruptus, p. p. of irrumpere to break in; pref. ir- in + rumpere to break or burst. See Rupture.] Broken with violence.

Ir*rup"tion (?), n. [L. irruptio: cf. F. irruption. See Irrupted.]

1. A bursting in; a sudden, violent rushing into a place; as, irruptions of the sea.

Lest evil tidings, with too rude irruption Hitting thy aged ear, should pierce too deep.

Milton.

2. A sudden and violent inroad, or entrance of invaders; as, the irruptions of the Goths into Italy. Addison.

Syn. -- Invasion; incursion; inroad. See Invasion.

Ir*rup"tive (?), a. Rushing in or upon.

Ir"ving*ite (?), n. (Eccl.) The common designation of one a sect founded by the Rev. Edward Irving (about 1830), who call themselves the Catholic Apostolic Church. They are highly ritualistic in worship, have an elaborate hierarchy of apostles, prophets, etc., and look for the speedy coming of Christ.

Is- (?). See Iso-.

Is (?), v. i. [AS. is; akin to G. & Goth. ist, L. est, Gr. &?;, Skr. asti. &radic;9. Cf. Am, Entity, Essence, Absent.] The third person singular of the substantive verb be, in the indicative mood, present tense; as, he is; he is a man. See Be.

In some varieties of the Northern dialect of Old English, is was used for all persons of the singular.

For thy is I come, and eke Alain.

Chaucer.

Aye is thou merry.

Chaucer.

The idiom of using the present for future events sure to happen is a relic of Old English in which the present and future had the same form; as, this year Christmas is on Friday.

To-morrow is the new moon.

1 Sam. xx. 5.

{ Is"a*bel (?), n., Is"a*bel col"or (?). } [F. isabelle.] See Isabella.

{ Is`a*bel"la (?), n., Is`a*bel"la col"or (?) }. [Said to be named from the Spanish princess Isabella, daughter of king Philip II., in allusion to the color assumed by her shift, which she wore without change from 1601 to 1604, in consequence of a vow made by her.] A brownish yellow color.

Is`a*bel"la grape` (?). (Bot.) A favorite sweet American grape of a purple color. See Fox grape, under Fox.

Is`a*bel"la moth` (?; 115). (Zoöl.) A common American moth (Pyrrharctia isabella), of an isabella color. The larva, called woolly bear and hedgehog caterpillar, is densely covered with hairs, which are black at each end of the body, and red in the middle part.

Is`a*bel"line (?), a. Of an isabel or isabella color.

Is*ag"e*lous (s*g"*ls), a. [Is- + Gr. a`gelos information.] Containing the same information; as, isagelous sentences. "The coded message and the original, though appearing entirely unlike, are completely isagelous." Bacon "The complementary strands have isagelous sequences." J. D. Watson. -- Is"a*gel n. One of two or more objects containing the same information.

I"sa*goge (?), n. [L., fr. Fr. &?;, fr. &?; to introduce; &?; into + &?; to lead.] An introduction. [Obs.] Harris.

{ I"sa*gog"ic (?), I"sa*gog"ic*al (?), } a. [L. isagogicus, Gr. &?;.] Introductory; especially, introductory to the study of theology.

I"sa*gog"ics (?), n. (Theol.) That part of theological science directly preliminary to actual exegesis, or interpretation of the Scriptures.

I"sa*gon ("s*gn), n. [Gr. 'i`sos equal + gwni`a angle: cf. F. isagone, a.] (Math.) A figure or polygon whose angles are equal.

Is*ap`os*tol"ic (?), a. [Gr. &?;.] Having equal, or almost equal, authority with the apostles of their teachings.

{ I*sat"ic (?), I`sa*tin"ic (?), } a. (Chem.) Pertaining to, or derived from, isatin; as, isatic acid, which is also called trioxindol.

I"sa*tide (?), n. (Chem.) A white crystalline substance obtained by the partial reduction of isatin. [Written also isatyde.]

I"sa*tin (?), n. [See Isatis.] (Chem.) An orange-red crystalline substance, C8H5NO2, obtained by the oxidation of indigo blue. It is also produced from certain derivatives of benzoic acid, and is one important source of artificial indigo. [Written also, less properly, isatine.]

||I"sa*tis (?; 277), n. [L., a kind of plant, Gr. &?; woad.] (Bot.) A ||genus of herbs, some species of which, especially the Isatis ||tinctoria, yield a blue dye similar to indigo; woad. || I*sat"o*gen (?), n. [Isatin + -gen.] (Chem.) A complex nitrogenous radical, C8H4NO2, regarded as the essential residue of a series of compounds, related to isatin, which easily pass by reduction to indigo blue. -- I*sat`o*gen"ic (#), a.

I`sa*trop"ic (?), a. [Is- + atropine.] (Chem.) Pertaining to, or designating, an acid obtained from atropine, and isomeric with cinnamic acid.

Is"chi*ac (s"k*k), a. (Anat.) See Ischial.

Is`chi*ad"ic (s`k*d"k), a. [L. ischiadicus, Gr. 'ischiadoko`s, fr. 'ischi`on the hip joint, hip or loin. Cf. Sciatic.] (Anat.) Ischial. [R.]

Ischiadic passion or disease (Med.), a rheumatic or neuralgic affection of some part about the hip joint; -- called also sciatica.