Verrius Flaccus, Marcus (märˈkəs vĕrˈēəs flăkˈəs) [key], fl. 20 B.C., Roman grammarian. A freedman, he was appointed by Augustus to educate his grandsons and died at an advanced age during the reign of Tiberius. Of his numerous works, only one, his treatise De verborum significatu [on the meaning of words], survives, in an abridgment by Sextus Pompeius Festus. This work is a source of information about Latin grammar and Roman literature, customs, and myths.