1. A cloth of exceedingly fine texture, used by the ancients. It is disputed whether it was of cotton, linen, or silk.
alternative forms: byss and byssin.
2. (Science: marine biology) 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. (Science: botany) An obsolete name for certain fungi composed of slender threads.
Origin: L. Byssus fine flax, fine linen or cotton, gr.