The Collaborative International Dictionary of English v.0.48:
Lugsail \Lug"sail`\, n. (Naut.) A square sail bent upon a yard that hangs obliquely to the mast and is raised or lowered with the sail. --Totten. [1913 Webster]WordNet (r) 3.0 (2006):
lugsail n 1: a sail with four corners that is hoisted from a yard that is oblique to the mast [syn: lugsail, lug]