1620s, from Latin veto, literally "I forbid," first person singular present indicative of vetare "forbid," of unknown origin. Used by Roman tribunes who opposed measures of the Senate or magistrates.
1706, from veto (n.). Related: Vetoed; vetoing.
The power of a president or governor to reject a bill proposed by a legislature by refusing to sign it into law. The president or governor actually writes the word veto (Latin for “I forbid”) on the bill and sends it back to the legislature with a statement of his or her objections. The legislature may choose to comply by withdrawing or revising the bill, or it can override the veto and pass the law, by a two-thirds vote in each house.
Note: Originally intended to prevent Congress from passing unconstitutional laws, the veto is now used by the president as a powerful bargaining tool, especially when his objectives conflict with majority sentiment in Congress. (See also checks and balances.)