Byssus

Part of speech: noun (n.)

1. A cloth of exceedingly fine texture, used by the ancients. It is disputed whether it was of cotton, linen, or silk. [Written also byss and byssin.]

2. A tuft of long, tough filaments which are formed in a groove of the foot, and issue from between the valves of certain bivalve mollusks, as the Pinna and Mytilus, by which they attach themselves to rocks, etc.

3. An obsolete name for certain fungi composed of slender threads.

4. Asbestus.