The term 'Heckler's Veto', occasionally mentioned in Supreme Court observations related to freedom of speech, refers to:

1. AThe power of a parliamentary whip to disqualify a legislator.
2. BA presidential power to veto a bill without providing a reason.
3. CA procedural tool used by the Speaker to silence a member of the house.
4. DA situation where an acting or threatening crowd succeeds in silencing a speaker.