- any of numerous small, wingless bloodsucking insects of the order Siphonaptera, parasitic upon mammals and birds and noted for their ability to leap.
- either of two common fleas of the genus Ctenocephalides, the very small, black C. felis(cat flea ) or the similar but larger C. canis(dog flea ), both of which infest cats, dogs, and occasionally humans.
- any of various small beetles and crustaceans that leap like a flea or swim in a jumpy manner, as the water flea and beach flea.
- flea in one's ear,
- a disconcerting rebuke or rebuff: The next time he shows his face around here he'll get a flea in his ear.
- a broad hint.
- any small wingless parasitic blood-sucking insect of the order Siphonaptera, living on the skin of mammals and birds and noted for its power of leaping
- any of various invertebrates that resemble fleas, such as the water flea and flea beetle
- a sharp rebuke
