Pronunciation: (mā'flī"),[key] —n., —pl.-flies. 1. Also called shadfly. any insect of the order Ephemeroptera, having delicate, membranous wings with the front pair much larger than the rear and having an aquatic larval stage and a terrestrial adult stage usually lasting less than two days.
2. Also,May' fly".Angling.an artificial fly made to resemble this insect.