The Collaborative International Dictionary of English v.0.48:

Nassa \Nas"sa\, n.; pl. E. Nassas, L. Nassae. [From L. nassa
   a kind of basket, in allusion to the reticulation of some
   species.] (Zool.)
   Any species of marine gastropods, of the genera Nassa,
   Tritia, and other allied genera of the family Nassidae; a
   dog whelk. See Illust. under Gastropoda.
   [1913 Webster] -- nas"soid, a.
   [1913 Webster]