Definition of "irregular"
adjective
comparative more irregular, superlative most irregular
without symmetry, regularity, or uniformity
Quotations
Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus) undergo an irregular, nomadic type of nocturnal migration.
2013 January 1, Paul Bartel, Ashli Moore, “Avian Migration: The Ultimate Red-Eye Flight”, in American Scientist, volume 101, number 1, pages 47–48