—n. 1. a projecting rim, collar, or ring on a shaft, pipe, machine housing, etc., cast or formed to give additional strength, stiffness, or supporting area, or to provide a place for the attachment of other objects.
2. a broad ridge or pair of ridges projecting from the edge of a rolled metal shape generally at right angles, in order to strengthen or stiffen it.
3. a ring or collar, usually provided with holes for bolts, and screwed or welded over the end of a tube or pipe to permit other objects to be attached to it.
4. (in plumbing) a plate or flat ring bolted to the flange at the end of a length of pipe to close the end or to connect it with the flange of another such length: blind flange; spectacle flange.
—v.i. to project like, or take the form of, a flange.