Definition of: irregular

(i·reg′yə·lər) adjective
1. Not regular; departing from or being out of the usual or proper form, order, course, method, proportion, etc.
2. Not conforming in action or character to rule, duty, discipline, etc.; lawless: irregular habits.
3. Bot. Exhibiting a want of symmetry in form and size: said of flowers in which the members of the various whorls differ from one another in size or shape.
4. Laboring under an ecclesiastical irregularity. See IRREGULARITY (def. 2).
5. Not belonging to a regular military force: irregular troops.
6. Gram. Not inflected or conjugated according to the most prevalent pattern: irregular verbs. See STRONG (def. 28).
7. Law Not according to rule; improper; not complying with legal formalities.
—noun A person exercising a calling or profession without belonging to its regular organization or conforming to its regulations, as a soldier not in a regular military force. [<OF irreguler <Med. L irregularis]
—ir·reg′u·lar·ly adverb Synonyms (adj.): abnormal, anomalous, confused, crooked, desultory, devious, disorderly, dissolute, eccentric, erratic, exceptional, fitful, immoderate, inordinate, uneven, unnatural, unsettled, unsymmetrical, unsystematic, unusual, variable, vicious, wandering, wild. Antonyms: common, constant, established, fixed, formal, methodical, natural, normal, orderly, ordinary, periodical, punctual, regular, stated, steady, systematic, uniform, universal, unvarying, usual.