Byssus \Bys"sus\, n.; pl. E. Byssuses; L. Byssi.[L. byssus
   fine flax, fine linen or cotton, Gr. by`ssos .]
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   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.]
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   2. (Zool.) 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.
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   3. (Bot.) An obsolete name for certain fungi composed of
      slender threads.
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   4. Asbestus.
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