insane Definition

insane
adj insaner, insanest

1. Said of a person: not of sound mind; mentally ill.

Thesaurus: deranged, crazy, lunatic, crazed, frenzied, maniacal, nuts (slang), demented, raving, mentally unsound, mentally disturbed, psychotic, schizophrenic, paranoid, wacko (slang).
2. colloq
Said especially of actions: extremely foolish; stupid.
Thesaurus: foolish, stupid, idiotic, madcap.
3. Belonging or relating to, or for, the mentally ill.

Example: an insane asylum
4. Insane people as a group (see the 4b).

Form: the insane

Derivative: insanely
adverb

Etymology: 16c: from Latin insanus.