lugsail

from 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}]

from 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]