flea -
A small, wingless, parasitic insect of the order Siphonaptera, renowned for its bloodsucking habits and jumping abilities.
flea -
A thing of no significance.
Wikipedia
Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood of mammals (including humans) and birds. In the past, it was most commonly supposed that fleas had evolved from the flies, based on similarities of the larvae.
OmegaWiki Dictionary
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flea Any of the wingless insects composing the order Siphonaptera; most are ectoparasites of mammals and birds.\n(Source: MGH)