na-adjective
Kansai dialect adjective meaning something is peculiar, off, or not right. Often carries a slightly negative or suspicious tone.
あの店の雰囲気、なんかけったいなあ。
The atmosphere of that shop is kind of weird, isn't it?
けったいな話やけど、ほんまにあったことやで。
It's a bizarre story, but it really happened.
Kansai dialect word; the exact origin is uncertain, but it may be related to the stem けったい- from the verb けったう (to kick) or a sound-symbolic formation.