English

Adjective

ultradian ‎(comparative more ultradian, superlative most ultradian)

1. Cyclical with a periodicity significantly shorter than 24 hours, that is, more frequent than circadian.
   • 1999, Evie Bentley, Awareness: Biorhythms, Sleep and Dreaming, page 15

     Ultradian rhythms […] operate in cycles of less than 24 hours, that is they happen more than once a day.

See also

• infradian