Definitions
1.NounA political right to disapprove of (and thereby stop) the process of a decision, a law etc.
2.NounAn invocation of that right.
3.NounAn authoritative prohibition or negative; a forbidding; an interdiction.
4.NounA technique or mechanism for discarding what would otherwise constitute a false positive in a scientific experiment.
5.VerbTo use a veto against."The president vetoed the bill."
6.VerbTo countermand."Mom and Dad vetoed our menu preferences for the holiday meal."