adverb taking the 'to' particle, adverb
slowly and quietly; stealthily
Describes moving in a slow, careful, and quiet manner so as not to be noticed. Often used with verbs of movement.
See also: そろり
泥棒はそろりそろりと窓から侵入した。
The thief crept in slowly and quietly through the window.
赤ちゃんが起きないように、そろりそろりと部屋を出た。
I left the room slowly and quietly so as not to wake the baby.
Reduplication of the mimetic adverb そろり, which itself represents slow, quiet movement. The exact origin is uncertain, but it is a sound-symbolic word.