irregular

American  

[ih-reg-yuh-ler] / ɪˈrɛg yə lər /

adjective

1. without symmetry, even shape, formal arrangement, etc..

   an irregular pattern.

   Synonyms:

   uneven, unsymmetrical

2. not characterized by any fixed principle, method, continuity, or rate.

   irregular intervals.

   Synonyms:

   lawless, eccentric, erratic, capricious, disorderly, unsystematic, unmethodical

3. not conforming to established rules, customs, etiquette, morality, etc..

   highly irregular behavior.

4. not according to rule, or to the accepted principle, method, course, order, etc.

   Synonyms:

   unusual, anomalous

5. 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.

6. Military. (formerly, of troops) not belonging to an organized group of the established forces.

7. flawed, damaged, or failing to meet a specific standard of manufacture.

   a sale of irregular shirts.

8. Botany.

   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.

9. deviating or experiencing deviations from a normally regular or cyclic body function, as bowel habits or menstruation.

10. (of a stock or commodity market) of mixed market activity; showing no clear up or down trend.

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noun

1. a person or thing that is irregular.

2. Commerce. a product or material that does not meet specifications or standards of the manufacturer, as one having imperfections in its pattern.

3. Military. a soldier or combatant not of a regular military force, as a guerrilla or partisan.

irregular British  

/ ɪˈrɛɡjʊlə /

adjective

1. lacking uniformity or symmetry; uneven in shape, position, arrangement, etc

2. not occurring at expected or equal intervals

   an irregular pulse

3. differing from the normal or accepted practice or routine

4. not according to established standards of behaviour; unconventional

5. (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

6. of or relating to guerrillas or volunteers not belonging to regular forces

   irregular troops

7. (of flowers) having any of their parts, esp petals, differing in size, shape, etc; asymmetric

8. (of merchandise) not up to the manufacturer's standards or specifications; flawed; imperfect

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noun

1. a soldier not in a regular army

2. (often plural) imperfect or flawed merchandise Compare second 1

Synonym Usage

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).

Other Word Forms

Derived Forms

• quasi-irregular
  adjective
• quasi-irregularly
  adverb
• irregularly
  adverb

Etymology

Origin of irregular

First recorded in 1350–1400; from Late Latin irrēgulāris ( see ir- ², regular); replacing Middle English irreguler, from Middle French

Explanation

Irregular describes something that's unpredictable or uneven. If your dog has irregular spots, it means that she has random splotches of color scattered across her fur. Anything that doesn't have a pattern or schedule is irregular, like the irregular hours of a store that's only open when the owner feels like it. In grammar, an irregular part of speech is one that doesn't stick to the usual rules. Irregular can also describe something doesn't meet standards, like irregular clothing that's sold at a discount. Irregular originally meant "not in conformity with Church rules."

Example Sentences

Irregular border crossings into the EU detected by authorities fell by 40 percent in the first four months of 2026 compared with the same period last year, according to the EU's border control agency.

From Barron's • Jun. 1, 2026

“We have a very finite number of certain munitions,” said Daniel Byman, the director of the Warfare, Irregular Threats and Terrorism Program at the Center for Strategic and International Studies.

From The Wall Street Journal • Mar. 2, 2026

Irregular arrivals into the UK are up 27% on the previous year, and the vast majority of these are via small boat.

From BBC • Oct. 26, 2025

Apple's Irregular Rhythm Notification and ECG app are cleared by the Food and Drug Administration for use by people 22 years of age or older.

From Science Daily • Dec. 13, 2023

Irregular warfare is war in which one or more sides might not use a regular military organization, and might or might not use conventional weapons or tactics.

From "An Indigenous People’s History of the United States" by Roxanne Dunbar-Ortiz

Related Words

• capricious
• erratic
• intermittent
• jerky
• sporadic
• uneven
• unreliable