n pl :  a family of freshwater pulmonate snails having a single pair of tentacles with an eye at the base of each and gills as well as lungs and including numerous forms important as intermediate hosts of pathogenic trematode worms - see PLANORBIS  pla*nor*bid adj or n 
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2008.