adverb, adverb taking the 'to' particle
smoothly; swiftly; without hindrance
Describes a motion that is quick, smooth, and unimpeded, often with a sense of slipping or sliding through effortlessly. Can be used with と.
猫がするりと塀を越えた。
The cat slipped smoothly over the fence.
彼はするりと人混みを抜けた。
He slipped through the crowd without any trouble.
Mimetic word; the exact origin is uncertain, but it likely derives from the sound-symbolic root suru- suggesting smooth sliding or slipping.