1 [more irregular; most irregular] : not normal or usual : not following the usual rules about what should be done
His behavior as a teacher was highly irregular.
Her application was handled in an irregular manner.
2 [more irregular; most irregular] : not even or smooth : not regular in form or shape
an irregular outline
a very jagged, irregular surface
The stone has an irregular shape.
3 [more irregular; most irregular] a : happening or done at different times that change often
She has been working irregular hours. [=she has been working for different amounts of time and at different times on different days]
He has a very irregular schedule.
b : not happening at times that are equally separated
The festival has been held at irregular intervals.
an irregular heartbeat