Source : Webster's Revised Unabridged Dictionary (1913)

Gasket \Gas"ket\, n. [Cf. F. garcette, It. gaschetta, Sp. cajeta
   caburn, garceta reef point.]
   1. (Naut.) A line or band used to lash a furled sail
      securely. {Sea gaskets} are common lines; {harbor gaskets}
      are plaited and decorated lines or bands. Called also
      {casket}.

   2. (Mech.)
      (a) The plaited hemp used for packing a piston, as of the
          steam engine and its pumps.
      (b) Any ring or washer of packing.

Source : WordNet®

gasket
     n : seal consisting of a ring for packing pistons or sealing a
         pipe joint