Origin of irregular

1350–1400; < Late Latin irrēgulāris (see ir-2, regular); replacing Middle English irreguler < Middle French
Related formsir·reg·u·lar·ly, adverbqua·si-ir·reg·u·lar, adjectivequa·si-ir·reg·u·lar·ly, adverb

Synonyms for irregular

1. unsymmetrical, uneven. 2. unmethodical, unsystematic; disorderly, capricious, erratic, eccentric, lawless. 4. anomalous, unusual. Irregular, abnormal, exceptional imply a deviation from the regular, the normal, the ordinary, or the usual. Irregular, not according to rule, refers to any deviation, as in form, arrangement, action, and the like; it may imply such deviation as a mere fact, or as regrettable, or even censurable. Abnormal means a deviation from the common rule, often implying that this results in an aberrant or regrettably strange form or nature of a thing: abnormal lack of emotion; A two-headed calf is abnormal. Exceptional means out of the ordinary or unusual; it may refer merely to the rarity of occurrence, or to the superiority of quality: an exceptional case; an exceptional mind. Because of the stigma of abnormal, exceptional is today frequently substituted for it in contexts where such a euphemism may be thought to be appropriate: a school for exceptional children (children who are abnormal in behavior, mental capacity, or the like). Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for irregular

Contemporary Examples of irregular

Historical Examples of irregular

  • But Mr. Paine assured her that letters were likely to be irregular, and there was no ground for alarm.

    Brave and Bold

    Horatio Alger

  • The advance may be irregular but it is advance; and all advance is advance toward Him.

  • He was furious at this supposition that she would continue in her irregular practices.

    Within the Law

    Marvin Dana

  • The enemy, surprised, opened an irregular and ineffective fire.

  • I design it an irregular ode for General Washington's birth-day.

British Dictionary definitions for irregular



lacking uniformity or symmetry; uneven in shape, position, arrangement, etc
not occurring at expected or equal intervalsan irregular pulse
differing from the normal or accepted practice or routine
not according to established standards of behaviour; unconventional
(of the formation, inflections, or derivations of a word) not following the usual pattern of formation in a language, as English plurals ending other than in -s or -es
of or relating to guerrillas or volunteers not belonging to regular forcesirregular troops
(of flowers) having any of their parts, esp petals, differing in size, shape, etc; asymmetric
US (of merchandise) not up to the manufacturer's standards or specifications; flawed; imperfect


a soldier not in a regular army
(often plural) US imperfect or flawed merchandiseCompare second 1 (def. 15)
Derived Formsirregularly, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for irregular

late 14c., "not in conformity with Church rules," from Old French irreguler (13c., Modern French irrégulier), from Medieval Latin irregularis, from assimilated form of in- "not, opposite of" (see in- (1)) + Latin regularis (see regular (adj.)). General sense is from late 15c.


"a soldier not of the regular army," 1747, from irregular (adj.).

Online Etymology Dictionary, © 2010 Douglas Harper

irregular in Medicine




Not straight, uniform, or symmetrical, as facial features.
Of uneven rate, occurrence, or duration, as a heartbeat.
Deviating from a type; atypical.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.