irregularadj/ɪˈɹɛɡ.jʊ.lə/

• 1

  Nonstandard; not conforming to rules or expectations.

  • ‘ “It would be most irregular Grandpa!” says Miss Cecily frowning and tapping her foot. “Well, we’re a pretty irregular family so that’s neither here nor there,” says the old man, impish like. [...] ’
• 2

  Of a surface, rough.

• 3

  Without symmetry, regularity, or uniformity.

  • The hovel stood in the centre of what had once been a vegetable garden, but was now a patch of rank weeds. Surrounding this, almost like a zareba, was an irregular ring of gorse and brambles, an unclaimed vestige of the original common.
  • Near by, where the crystal clear River Llugwy is crossed by a bridge, stands a small and ancient church built of massive, irregular boulders.
• 4

  geometrymathematicssciencesOf a polygon, not regular; having sides that are not equal or angles that are not equal.

• 5

  geometrymathematicssciencesOf a polyhedron, whose faces are not all regular polygons (or are not equally inclined to each other).

• 6

  grammarhuman-scienceslinguisticsOf a word, not following the regular or expected patterns of inflection in a given language.

  • "Calves", "cacti", and "children" are irregular plurals.
  • "To buy" is an irregular English verb: its past simple and past participle tense is "bought".
• 7

  gastroenterologymedicinesciencesHaving abnormal bowel movements at inconsistent intervals.

irregularnoun/ɪˈɹɛɡ.jʊ.lə/

• 1

  A soldier who is not a member of an official military force and who may not use regular army tactics.

• 2

  One who does not regularly attend a venue.

  • There's one neighborhood tavern where the regulars and irregulars go after a hard day to unlax and rewind, throw back a few, and just hang out - you know the one.