During a filibuster, a senator or group of senators continue to talk, often about irrelevant topics (reading the telephone book is a phrase often used), in order to prevent a vote on a particular subject. The rules of the US Senate allow for unlimited debate. So as long as the vocal cords of the senators hold out, they can prevent legislation from moving forward. The term is technically not restricted to the US Senate, but given the peculiar rules of this body it is most often used in reference to that body.
A filibuster is so-called because the minority hijacks the debate, much like a pirate hijacks a ship and it is an affront to good order and discipline, just like the Yankee filibusters who invaded Latin America in the 1850s.
Copyright 1997-2016, by David Wilton