irregular

American  

[ih-reg-yuh-ler] / ɪˈrɛg jə 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

• irregulars
  plural

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
• irregularly
  adverb
• quasi-irregularly
  adverb

Inflected Forms

Nouns

• irregulars
  plural

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

See Examples For:

irregular irregulars

The “All Night Long” singer-songwriter was hospitalized to receive treatment for an irregular heartbeat.

From Los Angeles Times ● Sep. 22, 2026

These included changes in menstruation such as bleeding between periods, heavy bleeding, and irregular menstrual cycles.

From Science Daily ● Sep. 13, 2026

The 29-year-old's ablation procedure - a minimally invasive operation to correct irregular heart rhythms - took place at Spire Manchester Hospital on Tuesday morning.

From BBC ● Sep. 8, 2026

Patel called the Nature paper “an important study” because the participants were actively experiencing medical conditions that can affect sleep, such as insomnia, and said “we need more” research on how wearables affect irregular sleepers.

From The Wall Street Journal ● Sep. 6, 2026

Geeks keep their computers on round-the-clock and often work irregular hours, in part because Web-surfing, software trading, and collecting and ICQ and Hotline messaging are factored in.

From "Geeks: How Two Lost Boys Rode the Internet Out of Idaho" by Jon Katz

Of the distinct combats that historians have identified, more than 90% were not primarily fought by formally organized regular troops but instead involved district militias and other irregulars, including Native American warriors.

From The Wall Street Journal ● Jan. 9, 2026

A small percentage of galaxies with more disorganized shapes are classified as irregulars.

From Textbooks ● Oct. 13, 2016

Then he materialized, followed by a raggle-taggle army, Muhammad Ali’s irregulars, your basic rainbow coalition of the late 1960s, falling in step behind him, chanting: “Muhammad Ali is our champ! Muhammad Ali is our champ!”

From New York Times ● Jun. 4, 2016

Smith called some of the guys irregulars because they were working full-time and could not commit themselves to building the houses full-time.

From Washington Times ● Mar. 14, 2015

Other clusters with a far more disordered geometry have, comparatively, many more spirals and irregulars.

From "Cosmos" by Carl Sagan

Related Words

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