Relating to biologic variations or rhythms occurring in cycles less frequent than every 24 hours. Cf.:circadian, ultradian. [infra- + L. dies, day]
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in·fra·di·an in-'frā-dē-ən adj being, characterized by, or occurring in periods or cycles (as of biological activity) of less than 24 hours <\infradian rhythms of growth> compare CIRCADIAN, ULTRADIAN
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in·fra·di·an (in″frə-deґən) [infra- + L. dies day] pertaining to the rhythmic repetition of certain phenomena in living organisms occurring in cycles of less frequency than circadian, that is, less frequently than once a day. Cf. circadian and ultradian.Medical dictionary. 2011.