1. A form of insanity, characterized by epilepsy and catalepsy.
2. An abnormal condition often associated with schizophrenia and variously characterized by stupor, stereotypy, mania, and either rigidity or extreme flexibility of the limbs.
3. A sever psychiatric condition, a syndrome, especially of schizophrenia, marked by stupor (depression), or catalepsy (a trancelike state with loss of voluntary motion and failure to react to stimuli); often alternating with phases of excitement (short periods of extreme agitation or movements).
4. A neuropsychiatric disorder characterized by one or more of the following essential features: immobility, mutism, negativism (active or passive refusal to follow commands), mannerisms, stereotypies, posturing, grimacing, excitement, echolalia, echopraxia, muscular rigidity, and stupor; sometimes punctuated by sudden violent outbursts, panic, or hallucinations.