byssus

noun, plural bys·sus·es, bys·si [bis-ahy] /ˈbɪs aɪ/.

1. Zoology. a collection of silky filaments by which certain mollusks attach themselves to rocks.
2. an ancient cloth, thought to be of linen, cotton, or silk.

noun plural byssuses or byssi (ˈbɪsaɪ)

1. a mass of strong threads secreted by a sea mussel or similar mollusc that attaches the animal to a hard fixed surface