n. In a constitutional government, the right vested in one branch of it to negative the determinations of another branch; specifically, the right, under constitutional restrictions, of the executive, as a king, a president, or a governor, to reject a bill passed, by the legislature; also, the act of exercising this right.n. Any right or power of authoritatively forbidding or effectively negativing, or the exercise of such right or power; prohibition; interdict.To forbid authoritatively; specifically, to negative by exercising the constitutional right of veto: as, to veto a bill.