n.any of several types of very small (about 1/4 inch or 0.6
cm), biting or nonbiting two-winged flies found in most parts of the
world. Some gnats feed off the blood of animals or humans and inflict a painful
bite. They have a tubelike mouth they
use to pierce the skin of their
victim and suck their blood. Gnats often
group into swarms that make a humming
sound. Because of their small size, they are sometimes used as an
analogy when describing minute quantities, size and so forth.