Definition of ultradian in English:



  • (of a rhythm or cycle) having a period of recurrence shorter than a day but longer than an hour.

    Compare with infradian
    • ‘In addition, the timing of an ultradian rhythm, the defecation cycle, is lengthened compared to wild type.’
    • ‘Still slower ultradian rhythms, with a period of 2 h, and circadian rhythms have also been observed.’
    • ‘Failure to synchronize your patterns of activity and stimulation with your body's natural circadian and ultradian rhythms puts a stress on the system.’
    • ‘These rhythmic contractions represent an ultradian cycle in worms that repeats every 47-50 sec and is controlled through inositol trisphosphate receptors in the posterior gut cells.’
    • ‘In the book Rossi provides essential historical data along with two of the author's favorite topics, ultradian rhythms and the four-stage creative cycle of healing and problem resolution.’


1960s: from ultra- beyond (being of greater frequency than circadian) + -ian.