An interjection expressing surprise, fear, pain, excitement, disgust, etc. Commonly used as a short exclamation in manga or speech.
きゃっ！虫が飛んできた。
Eek! A bug flew over.
キャー！プレゼントだ、嬉しい！
Yay! A present — I'm so happy!
ぎゃっ、と足をぶつけて痛がった。
He cried 'gya!' when he hit his foot and it hurt.
An onomatopoeic/mimetic word for a cry or screech (e.g., a monkey's screech).
森で猿がきゃっと鳴くのが聞こえた。
I heard a monkey give a sharp 'kya' in the forest.
Slang/thieves' cant meaning a customer (rare).
古い記録にきゃっ（客）を表す隠語として使われている例がある。
There are examples in old records of 'kya' being used as slang for a customer.