- any of various small crustaceans that move about in the water like fleas, as those of the genus Daphnia.
Origin of water flea
First recorded in 1575–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for water flea
In short, she was a branchiopod, to be vulgarly precise, a water-flea."Wee Tim'rous Beasties"
I have already spoken of the fresh-water shrimp and the water-flea (Daphnia pulex).Amateur Fish Culture
Charles Edward Walker
The water-flea, Daphnia (a crustacean), lays two kinds of eggs known as “summer” and “winter” eggs.
- any of numerous minute freshwater branchiopod crustaceans of the order Cladocera, which swim by means of hairy branched antennaeSee also daphnia