/ ɪˈregjələ(r); NAmE / adjective , noun
■ adjective
1.
not arranged in an even way; not having an even, smooth pattern or shape
SYN uneven :
irregular teeth
an irregular outline
2.
not happening at times that are at an equal distance from each other; not happening regularly :
irregular meals
an irregular heartbeat
irregular attendance at school
He visited his parents at irregular intervals .
3.
not normal; not according to the usual rules
SYN abnormal :
an irregular practice
His behaviour is highly irregular.
4.
( grammar ) not formed in the normal way :
an irregular verb
5.
( of a soldier etc. ) not part of a country's official army
OPP regular
► ir·regu·lar·ly adverb
■ noun
a soldier who is not a member of a country's official army
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WORD ORIGIN
late Middle English (in the sense not conforming to rule (especially that of the Church) ): via Old French from medieval Latin irregularis , from in- not + regularis (from regula rule).