adverb taking the 'to' particle
Mimetic adverb describing a short, sharp sound, especially a camera shutter click or a similar snapping noise. Often used with と.
カメラのシャッターがパチリと鳴った。
The camera shutter clicked.
彼はパチリと指を鳴らした。
He snapped his fingers.
Onomatopoeic word mimicking a short, sharp sound such as a click or snap. The exact origin is uncertain, but it is a conventional mimetic expression in Japanese.