To swing is to sway back and forth, or to move in a sweeping, curving motion. Wind chimes swing in the breeze, and a softball player swings her bat, aiming for the ball.
A TV hypnotist will swing a shiny object in front of a patient's face and say, "You are getting very sleepy." Kids on a playground will happily swing on swings for hours. And if you hear a sudden scary noise behind you, you might swing around in alarm or even take a swing, or a punch, in its direction. Since 1933, the noun swing has also meant a type of big-band jazz music.