Noun

1. Any mechanical seal that serves to fill the space between two objects, generally to prevent leakage between the two objects while under compression.
2. 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
3. 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