1. Adverb taking the 'to' particle, Noun

   with a snap; with a flick; with a clack; with a whap

   Onomatopoeic or mimetic word

   母はぱちっとハンドバッグを閉めた。

2. wide-eyed; with a flick (of eyelids); with a blink; opened wide (of eyes)

   Onomatopoeic or mimetic word

3. with a crackle (of a fire); with a rustle; with a burst

   Onomatopoeic or mimetic word

Also written ぱちっpachitsu