This is a procedural tactic to block or delay legislation used predominantly in the United States Senate.

A filibuster usually involves a senator or group of senators talking for hours or days to prevent a final vote on a bill. Overcoming a filibuster requires a cloture motion, which must be passed by three-fifths of the senate - usually 60 senators. These days, actual filibusters are rarely carried out, but the threat of them is enough to force a cloture vote.