Wiktionary
n. (context nautical English) a sailing rig that has a fore-and-aft sail supported by a spar called a gaff
Wikipedia
Gaff rig is a sailing rig (configuration of sails, mast and stays) in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the gaff. Because the size and shape of the sail, a gaff rig will have running backstays rather than permanent backstays.
The gaff enables a fore and aft sail to be four sided, rather than triangular. A gaff rig typically carries 25 percent more sail than an equivalent bermudian rig for a given hull design.
A sail hoisted from a gaff is called a gaff-rigged (or, less commonly, gaff rigged or gaffrigged) sail.
Usage examples of "gaff rig".
A tall mast and a gaff rig changed her into something much more graceful than she had been with a diesel stuck on her stern.
The sails were different as well, a gaff rig for this schooner as opposed to the dromond's lateen.