Adverb (fukushi), Adverb taking the 'to' particle
slapping; splashing; splatting; banging shut; flat (refusal, denial, etc.)
Onomatopoeic or mimetic word
彼の無礼な返事に彼女はかっとなって彼の顔をぴしゃりとたたいた。His rude reply provoked her to slap him on the face.
Also written ピシャリ