forestay

from WordNet (r) 3.0 (2006)

forestay
    n 1: an adjustable stay from the foremast to the deck or
         bowsprit; controls the bending of the mast

from The Collaborative International Dictionary of English v.0.48

Forestay \Fore"stay`\, n. (Naut.)
   A large, strong rope, reaching from the foremast head to the
   bowsprit, to support the mast. See Illust. under {Ship}.
   [1913 Webster]