infradian

[ in-frey-dee-uhn ]

adjective

, Physiology.

1. of or relating to a biorhythm or regular biological cycle having a period of more than 24 hours, such as the migration of birds or the human menstrual cycle. Compare circadian ( def ), ultradian ( def ).

Word History and Origins

Origin of infradian¹

First recorded in 1965–70; infra- ( def ) + Latin di(ēs) “day” + -an ( def )