A Filibuster is a tactic used in the US Senate by both Republicans and Democrats. Sigh.

Origin
The word "filibuster" comes from the Spanish word "filibustero," meaning "pirate," or "buccaneer." Filibusters were authorized by a Senate Rule in the early 19th Century by Angry Conservatives who were unhappy that they couldn't silence the voice of the people easily enough.
Practice
Racist Republican s used fillibusters to try and stop African-Americans getting equality.
Filibusters were particularly useful to Southern senators who sought to block civil rights legislation, including anti-lynching legislation, until cloture was invoked after a fifty-seven day filibuster against the Civil Rights Act of 1964. In 1975, the Senate reduced the number of votes required for cloture from two-thirds to three-fifths, or sixty of the current one hundred senators. [1]
Filibusters are when a Senator stands up and begins to talk, and never stops. This delays bringing a bill to a floor vote that would obviously pass. They can be stopped only by a closure vote, which needs sixty yay's. Filibusters can be used constructively, if used sparingly, such as Mike Gravel's miraculous five-month filibuster to help end the draft during the Vietnam War.
Modern Use
In recent history, Senators stopped using talking filibusters, and just declared they wanted to fuilibuster a bill, and the bill was filibustered. Under Mitch McConnell, nearly every bill has been filibustered, so instead of needing 51 votes to pass a bill, you need 60, even though the U.S. Constitution calls for majority rule in the Senate except on certain issues, for example, impeachment.