すっと
すっと · sutto · JLPT N4 · adverb
quickly
sutto: su = a soft whoosh, tto = an abrupt stop. One swift, clean move.
Japanese sound-symbolic adverb. The breathy su mimics air slipping past with no resistance; the doubled t snaps it shut. So すっと means doing something in one smooth, quick, straight motion, like standing up or stepping forward without a hitch.