Source : Webster's Revised Unabridged Dictionary (1913)

Lateen \La*teen"\, a. (Naut.)
   Of or pertaining to a peculiar rig used in the Mediterranean
   and adjacent waters, esp. on the northern coast of Africa.
   See below.

   {Lateen sail}. [F. voile latine a sail in the shape of a
      right-angled triangle; cf. It. & Sp. vela latina; properly
      Latin sail. See {Latin}.] (Naut.) A triangular sail,
      extended by a long yard, which is slung at about one
      fourth of its length from the lower end, to a low mast,
      this end being brought down at the tack, while the other
      end is elevated at an angle or about forty-five degrees;
      -- used in small boats, feluccas, xebecs, etc., especially
      in the Mediterranean and adjacent waters. Some lateen
      sails have also a boom on the lower side.

Source : WordNet®

lateen sail
     n : a triangular fore-and-aft sail used especially in the
         Mediterranean [syn: {lateen}]