horsefly /ˈhoɹsˌflaɪ/ noun1 •Any of several medium to large flies, of the family Tabanidae, that suck the blood of mammals (not to be confused with Stomoxys calcitrans, the stable fly, or dog fly).It was not a horsefly and it was not a deerfly; it was bigger than either. — 2017 formshorseflies