having a shape, surface, pattern etc that is not even, smooth, or balanced [= uneven; ≠ regular]:
a jagged, irregular coastline
It has a highly irregular shape, covered in bumps and indentations.
not happening at times that are an equal distance from each other [≠ regular]:
He's receiving medication for an irregular heartbeat.
Beamish only returned to Britain at irregular intervals.
not happening or done at the normal time for doing something [≠ regular]:
Funeral directors often work long, irregular hours.
not obeying the usually accepted legal or moral rules:
It would be highly irregular (=extremely irregular) for a minister to accept payments of this kind.
a verb or a form of a word that does not follow the usual pattern of grammar, such as the verb 'catch' or the plural 'fish' [≠ regular]
6 American EnglishMI
a word meaning constipated (=unable to easily pass food waste from your body), used in order to be polite
—irregularity noun [uncountable and countable]
The club were found guilty of financial irregularities.