The Collaborative International Dictionary of English v.0.48:

catatonia \cat`a*ton"ia\ n. [Gr. katatonos, stretching down,
   depressed, fr. kata` down + to`nos stretching, straining,
   tone (sound). --Stedman.] (Psychiatry)
   an abnormal behavioral syndrome characterized by stupor,
   negativism, and muscular rigidity, sometimes alternating with
   purposeless excitement, and seen most frequently in
   schizophrenia; called also catatonic schizophrenia.
   [PJC]

WordNet (r) 3.0 (2006):

catatonia
    n 1: extreme tonus; muscular rigidity; a common symptom in
         catatonic schizophrenia
    2: a form of schizophrenia characterized by a tendency to remain
       in a fixed stuporous state for long periods; the catatonia
       may give way to short periods of extreme excitement [syn:
       catatonic schizophrenia, catatonic type schizophrenia,
       catatonia]