An informal term for any attempt to block or delay U.S. Senate action on a bill or other matter by debating it at length, by offering numerous procedural motions, or by any other delaying or obstructive actions.
From the Senate Historical Office: “Using the filibuster to delay or block legislative action has a long history. The term filibuster — from a Dutch word meaning ‘pirate’ — became popular in the 1850s, when it was applied to efforts to hold the Senate floor in order to prevent a vote on a bill.
“In the early years of Congress, representatives as well as senators could filibuster. As the House of Representatives grew in numbers, however, revisions to the House rules limited debate. In the smaller Senate, unlimited debate continued on the grounds that any senator should have the right to speak as long as necessary on any issue.”
Sen. Strom Thurmond (R-SC) holds the record for the longest filibuster in his attempt to block the 1957 Civil Rights bill. Though he held the floor for 24 hours and 18 minutes, the bill passed just two hours after he stopped talking.