A filibuster in the U.S. Senate is a procedural tactic that allows one or more senators to delay or obstruct legislative action by extending debate on a bill. Typically, a filibuster requires a supermajority of 60 votes to invoke cloture and end the debate, effectively enabling a minority to block legislation. This practice is often used to draw attention to specific issues or to leverage negotiations, playing a significant role in shaping legislative dynamics within the Senate.