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[ih-reg-yuh-ler] /ɪˈrɛg yə lər/
without symmetry, even shape, formal arrangement, etc.:
an irregular pattern.
not characterized by any fixed principle, method, continuity, or rate:
irregular intervals.
not conforming to established rules, customs, etiquette, morality, etc.:
highly irregular behavior.
not according to rule, or to the accepted principle, method, course, order, etc.
Grammar. not conforming to the prevalent pattern or patterns of formation, inflection, construction, etc., of a language; having a rule descriptive of a very small number of items:
The English verbs “keep” and “see” are irregular in their inflections.
Military. (formerly, of troops) not belonging to an organized group of the established forces.
flawed, damaged, or failing to meet a specific standard of manufacture:
a sale of irregular shirts.
  1. not uniform.
  2. (of a flower) having the members of some or all of its floral circles or whorls differing from one another in size or shape, or extent of union.
deviating or experiencing deviations from a normally regular or cyclic body function, as bowel habits or menstruation.
(of a stock or commodity market) of mixed market activity; showing no clear up or down trend.
a person or thing that is irregular.
Commerce. a product or material that does not meet specifications or standards of the manufacturer, as one having imperfections in its pattern.
Military. a soldier or combatant not of a regular military force, as a guerrilla or partisan.
Origin of irregular
1350-1400; < Late Latin irrēgulāris (see ir-2, regular); replacing Middle English irreguler < Middle French
Related forms
irregularly, adverb
quasi-irregular, adjective
quasi-irregularly, adverb
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 Dictionary, © Random House, Inc. 2017.
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Examples from the Web for irregular
Contemporary Examples
Historical Examples
  • The lodges were arranged in two irregular circles, one within the other.

    South from Hudson Bay E. C. [Ethel Claire] Brill
  • They should break the slopes and be irregular in size, shape, and distribution.

    Making A Rock Garden Henry Sherman Adams
  • The streets of the town could not be more tortuous and irregular.

    Corea or Cho-sen A (Arnold) Henry Savage-Landor
  • Its contents are brief, but written in a fine, irregular hand.

    Floyd Grandon's Honor Amanda Minnie Douglas
  • Wiegmann diversified as much as possible his mode of bringing about these irregular unions among plants.

    Principles of Geology Charles Lyell
British Dictionary definitions for irregular


lacking uniformity or symmetry; uneven in shape, position, arrangement, etc
not occurring at expected or equal intervals: an 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 forces: irregular 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 pl) (US) imperfect or flawed merchandise Compare second1 (sense 15)
Derived Forms
irregularly, 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
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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
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irregular in Medicine

irregular ir·reg·u·lar (ĭ-rěg'yə-lər)

  1. Not straight, uniform, or symmetrical, as facial features.

  2. Of uneven rate, occurrence, or duration, as a heartbeat.

  3. 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.
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