English Reference
adjective · noun

irregular

adj. · n.
US /ˌɪˈɹɛɡjəɫɝ/ UK /ɪɹˈɛɡjuːlɐ/ ir·reg·u·lar UK spelling irregulars

  1. 01 B2 Upper Intermediate

    adj.not happening at regular times or following a steady pattern.

    adj.occurring at uneven or varying intervals; lacking a predictable temporal or spatial pattern.

    Simple

    The doctor noticed that the patient had an irregular heartbeat.

    In context

    The company faced significant cash flow problems due to the irregular nature of their seasonal sales and unpredictable client payments.

  2. 02 B1 Intermediate Technical Science

    adj.a word that does not follow the usual rules for its endings.

    adj.not following the standard patterns of inflection or conjugation within a specific language system.

    Simple

    The verb 'to be' is the most irregular verb in the English language.

    In context

    Students often struggle with irregular past participle forms, as they must be memorised individually rather than generated through a rule-based suffix.

    Usage

    In linguistics, this usually refers to verbs, nouns, or adjectives that have unique forms.

    Pitfall
    The past tense of 'go' is a regular word. The past tense of 'go' is irregular.

    In grammar, 'irregular' is the specific term for words that do not follow the standard rules for endings like -ed.

    nonstandard
  3. 03 B2 Upper Intermediate Math

    adj.not having a smooth or balanced shape.

    adj.lacking symmetry, uniformity, or equal sides and angles.

    Simple

    The island has a very irregular coastline with many small bays.

    In context

    The architect designed the building around an irregular plot of land, resulting in a unique floor plan with no right angles.

  4. 04 C1 Advanced Formal

    n.a soldier who is not part of a country's official army.

    n.a member of an armed force that is not part of the official military establishment of a state.

    Simple

    The forest was filled with irregulars fighting against the invading army.

    In context

    The historical account details how a small band of irregulars managed to disrupt the supply lines of the professional imperial forces for several months.

It also proposes introducing military education in high schools and a “remigration” plan to remove irregular immigrants and foreign nationals who commit crimes.

The Guardian· 3 Sept 2026

So why is it taking Spain so long to decide what to do with the irregular migrants in Ceuta?

The Local· 3 Sept 2026

From Middle English irreguler, from Old French irreguler, from Medieval Latin or Late Latin irrēgulāris, from in- + regularis, equivalent to ir- + regular.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin la-lat irrēgulāris
Level B2 · Upper Intermediate
Frequency Frequent
Updated