adverb taking the 'to' particle
Describes something standing straight or extending flatly, often with と. Mimetic.
He straightened his back perfectly.
adverb taking the 'to' particle
sticking into; attaching quickly
Mimetic for a quick sticking or attaching motion. Often with と.
I stuck the sticker on quickly.
The thread snapped.
When the teacher pointed it out, I snapped my back straight.
He snapped the TV switch off.
I quickly stuck a sticker onto the envelope.
ぴたっと stresses a firm, close fit after attaching, while ぴっ focuses on the speed of the sticking motion itself.
Mimetic word; the exact origin is uncertain, but it is likely derived from the sound or sensation of a quick, sharp action.