A person suffering from or susceptible to nervous or mental disease. Cf. psychopath, n.

slang (originally U.S.). A worthless, stupid, insane, or wildly eccentric person. Cf. dingbat, n. 3.

U.S. A person with a mental disorder or a pathological compulsion.

colloquial (originally U.S.). A crazy, mad, or eccentric person; = nutcase, n.

A mad or crazy person; (also, occasionally) a violent person. Cf. nutcase, n.

One who is mentally ill.

A crazy, mad, or eccentric person. Cf. nutcase, n.

North American slang. One who is mentally ill or (regarded as) perverted. Also attributive or as adj.

= sickie, n. 2.

An eccentric or mentally unbalanced person; a crank, a lunatic. Cf. wacko, n.

= wackadoo, n.