water fleawater flea
- Any of various small chiefly freshwater branchiopod crustaceans of the order Cladocera, having a bivalve carapace and typically swimming with jerking flealike motions, and including the daphnias. Also called cladoceran .
- Any of various other small aquatic crustaceans, such as some copepods, that swim with a similar motion.
(plural water fleas)