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
   `Ultradian` characterizes recurrent periods or cycles repeated frequently throughout a 24-hour day The descriptive term ultradian is used in sleep research to describe individual stages of sleep that occur within intervals of an organism's circadian rhythm, and especially to refer to a 90 minute REM cycle in human sleep. Some of the ultradian cyclings of the body are hormonal release, heart rate, thermoregulation, nostril dilation and appetit...
   Found on http://en.wikipedia.org/wiki/Ultradian
   
   
3. 
   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.mercksource.com/pp/us/cns/cns
   
   
4. 
   ultradian
   Relating to biologic variations or rhythms occurring in cycles more frequent than every 24 hours. Cf. circadian, infradian [ultra- + L. dies, day]
   Found on