The Collaborative International Dictionary of English v.0.48:
Dipsas \Dip"sas\, n. [L., fr. Gr. ?, fr. ? thirst.]
1. A serpent whose bite was fabled to produce intense thirst.
--Milton.
[1913 Webster]
2. (Zool.) A genus of harmless colubrine snakes.
[1913 Webster]