spinnaker

from WordNet (r) 3.0 (2006)

spinnaker
    n 1: a large and usually triangular headsail; carried by a yacht
         as a headsail when running before the wind

from The Collaborative International Dictionary of English v.0.48

Spinnaker \Spin"na*ker\ (sp[i^]n"n[.a]*k[~e]r), n. (Naut.)
   A large triangular sail set upon a boom, -- used when running
   before the wind.
   [1913 Webster]