n.pl. (also treated as sing.)
1. a device with an air bag that emits a stream of air when squeezed, esp.: a (in full pair of bellows) a kind with two handles used for blowing air on to a fire. b a kind used in a harmonium or small organ.
2 an expandable component, e.g. joining the lens to the body of a camera.
Etymology: ME prob. f. OE belga pl. of belig belly