Nouns

(n)vetoa vote that blocks a decision
(n)vetothe power or right to prohibit or reject a proposed or intended act (especially the power of a chief executive to reject a bill passed by the legislature)

Verbs

(v)veto, blackball, negativevote against; refuse to endorse; refuse to assent“The President vetoed the bill”
(v)forbid, prohibit, interdict, proscribe, veto, disallow, nixcommand against“I forbid you to call me late at night”, “Mother vetoed the trip to the chocolate store”, “Dad nixed our plans”