also: きちげぇ
あんなことを言うなんて、きちがいじみている。
Saying something like that is crazy (literally: seems like madness).
When he gets angry, he turns into an uncontrollable madman.
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.
He's a workout fanatic and goes to the gym every day.
That person is a game maniac, so you'll get along.
He's a fishing nut and goes to the river every weekend.
He kept working like a madman.
基地 (as slang) is a softened, joking suffix meaning 'fanatic', while 気違い is the blunt, offensive original word for 'crazy person' that it comes from.
キチ is a clipped, somewhat softened slang suffix derived from 気違い, which is the full word literally meaning 'crazy person' and is far more offensive.
Katakana spelling; often used for emphasis or in informal writing. This is a priority reading.
Search-only kanji form; not a standard spelling.
Irregular kanji usage; a non-standard phonetic substitution. Included for search coverage only.
Irregular kanji usage; a non-standard phonetic substitution. Included for search coverage only.