Look up: ultradian

1. ultradian
   Relating to biologic variations or rhythms occurring in cycles more frequent than every 24 hours. ... Compare: circadian, infradian. ... Origin: ultra-+ L. Dies, day ... (05 Mar 2000) ...
   Found on http://www.mondofacto.com/facts/dictiona
   
   
2. ultradian
   (ul″trә-de´әn) pertaining to a period of less than 24 hours; applied to the rhythmic repetition of certain phenomena in living organisms occurring in cycles of less than a day. See also ultradian rhythm.
   Found on http://www.encyclo.co.uk/local/21001
   
   
3. ultradian
   Type: Term Pronunciation: ŭl-trā′dē-ăn Definitions: 1. Relating to biologic variations or rhythms occurring in cycles more frequent than every 24 hours.
   Found on http://www.medilexicon.com/medicaldictio
   
   
4. Ultradian
   `Ultradian` rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. In contrast, infradian rhythms, such as the human menstrual cycle, have periods longer than a day. The descriptive term ultradian is used in sleep research in reference to the 90–120 minute cyclin...
   Found on http://en.wikipedia.org/wiki/Ultradian