1.  tethys(n = noun.person) - (Greek mythology) a Titaness and sea goddess; wife of Oceanus;
is a kind of titaness

2.  tethys(n = noun.animal) aplysia, genus aplysia, genus tethus - type genus of the family Aplysiidae;
is a kind of mollusk genus
is a member of aplysiidae, family aplysiidae, family tethyidae, tethyidae

   A genus of a large naked mollusks having a very large, broad, fringed cephalic disk, and branched dorsal gills. Some of the species become a foot long and are brilliantly colored. [1913 Webster]