swish
A soft, smooth sound or motion made while moving quickly.
Swish is the soft, rushing sound something makes when it moves smoothly and quickly through the air or water. A basketball makes a satisfying swish when it drops through the net without touching the rim. Long skirts swish around someone's legs as they walk. You might hear the swish of windshield wipers, or the swish of a horse's tail batting away flies.
The word captures both the sound and the graceful movement that creates it. When a gymnast's ribbon swishes through the air during a routine, or when tree branches swish in the wind, there's something elegant and flowing about the motion. The sound itself is smooth and quick, not harsh or jarring.
You can also use swish as a verb: a cat swishes its tail when annoyed, or you might swish water around in your mouth after brushing your teeth. Basketball players dream of that perfect swish shot, and some people call it a swisher when the ball goes in without touching anything but net.