gasket

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of a wide variety of seals or packings used between matched machine parts or around pipe joints to prevent the escape of a gas or fluid.
• noun Nautical A cord or canvas strap used to secure a furled sail to a yard boom or gaff.

from The Century Dictionary.

• To fasten with gaskets, as a sail to a yard.
• noun Nautical, one of several bands of sennit or canvas, or small lines, used to bind the sails to the yards, gaffs, or masts when furled. Also called casket.
• noun In machinery, a strip of leather, tow, plaited hemp, or similar material, used for packing a piston, as of the steam-engine and its pumps.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.
• noun The plaited hemp used for packing a piston, as of the steam engine and its pumps.
• noun Any ring or washer of made of a compressible material, used to make joints impermeable to fluids.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any mechanical seal that serves to fill the space between two objects, generally to prevent leakage between the two objects while under compression.
• noun A material which may be clamped between faces and acts as a static seal. Gaskets may be cut, formed, or molded to the desired configuration. - ASTM
• noun Any of a wide variety of seals or packings used between matched machine parts or around pipe joints to prevent the escape of a gas or fluid. - American Heritage Dictionary

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun seal consisting of a ring for packing pistons or sealing a pipe joint