irregular

/ɪˈrɛɡjələr/
noun
  1. A person who is not part of a regular military force, such as a guerrilla or rebel fighter.
    • The army faced attacks from both regulars and irregulars in the mountainous terrain.
    • Irregulars often used hit-and-run tactics against the larger force.
    • Many irregulars joined the fight to defend their homeland.
adjective
  1. Not following the usual pattern, rule, or schedule; uneven or not regular.
    • Her heartbeat was irregular, so the doctor ordered more tests.
    • The surface of the old stone wall was rough and irregular.
    • The bus service is irregular on weekends, so check the timetable carefully.
  2. Not conforming to standard grammar rules, especially in verb forms or plurals.
    • The plural of "child" is "children," which is an irregular plural form.
    • English has many irregular nouns that don't follow the usual -s or -es pattern.
    • "Go" is an irregular verb because its past tense is "went," not "goed."
  3. Not part of a regular or official military force.
    • The region was controlled by various irregular militias.
    • Historians study the role of irregular soldiers in the revolution.
    • Irregular troops fought alongside the regular army during the conflict.