gnat n any of various small fragile biting dipterous insects of the suborder Nematocera, esp. Culex pipiens (common gnat), which abounds near stagnant water (Old English gnætt; related to Middle High German gnaz scurf, German dialect Gnitze gnat)
n any of various small North American blood-sucking dipterous insects of the genus Simulium and related genera: family Simuliidae, (Also called)
n an angler's name for the spinner of various mayflies, esp. Ephemeris danica and E. vulgata, particularly when lying spent on the water surface after mating and egg-laying
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