きちがい

noun

madness; insanity; crazy person; lunatic

Derogatory and highly sensitive term for mental illness or a person perceived as insane. Strongly offensive; avoid in polite conversation. Often used hyperbolically or as an insult.

• あんなことを言いうなんて、きちがいじみている。

  Saying something like that is crazy (literally: seems like madness).

• 彼かれは怒おこると手てがつけられないきちがいになる。

  When he gets angry, he turns into an uncontrollable madman.

noun, noun, used as a suffix

mania; craze; obsession; enthusiast; fanatic

Used as a suffix or standalone noun to indicate an extreme obsession or enthusiast. Often derogatory or self-deprecating, e.g., 釣りきちがい (fishing nut). Less sensitive than sense 1 but still informal and potentially offensive.

• 彼かれは筋きんトレきちがいで、毎まい日にちジムに通かよっている。

  He's a workout fanatic and goes to the gym every day.

• あの人ひとはゲームきちがいだから、話はなしが合あうよ。

  That person is a game maniac, so you'll get along.