Irritant \Ir"ri*tant\, a. [L. irritans, -antis, p. pr. of irritare: cf. F. irritant. See Irritate to excite.]

Irritating; producing irritation or inflammation.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Irritant \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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Irritant \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.

Source: Webster's Revised Unabridged Dictionary (1913)