physa

from The Century Dictionary.

• noun [lowercase] A pond-snail of the genus Physa.
• noun [lowercase; pl. physæ (-sē).] In some anthozoans, as Edwardsia, the lower end of the body. It may or may not be retractile into the scapus. Compare capitulum, 6, and scapus, 6.
• noun A large genus of pond-snails or fresh-water gastropods of the family Limnæidæ, or made type of the Physidæ, having the shell sinistral.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A genus of fresh-water Pulmonifera, having reversed spiral shells. See Pond snail, under pond.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun zoology Any of the genus Physa of freshwater snails.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any member of the genus Physa