1) Class of mollusks 
• (n.) One of the Pteropoda.
small marine gastropods of the subclass Opisthobranchia having a pair of winglike flaps (parapodia) that are used for swimming. These gastropods were ...
Pter'o·pod noun [ Greek ... wing-footed; ... a feather, wing + ..., ..., foot: confer French ptéropode .] (Zoology) One of the Pteropoda. 
pteropod Belonging or pertaining to mollusks having the lateral portions of the foot expanded into winglike lobes used for swimming.
belonging or pertaining to the Pteropoda, a group of mollusks having the lateral portions of the foot expanded into winglike lobes used in swimming.