Dictionary.net

• A genus of dipterous insects, family Tabanidae, of which T. bovinus, or gadfly, is the largest American species. It is extremely troublesome to cattle.

1899 - The american dictionary of the english language.
By Daniel Lyons

• A genus of bloodsucking flies of the Diptera and the family Tabanidae.

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe