I. plural noun — [also treated as sing.] 1. (also a pair of bellows) — a device with an air bag that emits a stream of air when squeezed together with two handles, used for blowing air into a fire. • stoking up the fire with the bellows.
2. a device similar to a pair of bellows used in a harmonium or small organ. 3. an object or device with concertinaed sides to allow it to expand and contract, such as a tube joining a lens to a camera body.
– origin Middle English: probably from Old English belga, plural of belig (see belly), used as a shortened form of earlier blǣstbelig ‘blowing bag’.