/ Dictionary / Index B black fly: Meaning and Definition of Find definitions for: black' fly" Pronunciation: [key] any of the minute, black gnats of the dipterous family Simuliidae, having aquatic larvae. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: blackfly (Thesaurus) black flux black fog Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language