Filibuster refers to the use of extreme tactics to delay action, especially in a legislative body. A filibuster often takes the form of continuous speeches on the floor of the legislative body, with the group opposing a final vote indicating their intent to speak indefinitely. Filibusters can take other forms depending on the situation, such as proposing endless amendments that extend debate endlessly. If a filibuster has been used, the group seeking a vote on the proposal then has to decide whether to drop the proposal, make agreements with the opposition, or pursue a procedural way to cut off debate.
In the U.S., the Senate notoriously has been prevented from passing legislation in modern history due to filibusters. While originally the Senate did not have a filibuster, the practice came into play in the early 19th century, and now, a single senator can filibuster a piece of legislation unless a two-thirds majority of the Senate agree to end the filibuster. Technically, a bill in the Senate can pass with a simple majority, but speaking must end before a vote can begin. Thus, senators in opposition to a bill can, given there is nothing limiting their ability to speak on the floor, can talk until the bill is withdrawn. If 41 or more senators threaten a filibuster, no one has to continuously give speeches at all anymore. Instead the bill will just be withdrawn. Given this procedural tool, most major pieces of legislation do not pass the Senate unless one of the many exceptions to the filibuster apply, such as for appropriations.
[Last updated in December of 2022 by the Wex Definitions Team]