Intent-to-filibuster refers to a "gentleman's agreement" reached several decades ago amongst the members of the US Congress. Under this agreement, it is no longer actually necessary to speak continually in order to enact a filibuster; all that is necessary is to announce your intention to filibuster, and the Majority Leader will follow through as if you were actually talking. This has the immediate effect of increasing the number of votes required in order to pass a motion.
This strikes me as being rather like Arthur Dent announcing his intention to lie down in front of the bulldozer to prevent it knocking down his house – and then getting the bulldozer operator to agree that since he knew Arthur was going to be there all day, he didn't actually need Arthur to be there, and would agree not to knock down Arthur's house whilst Arthur went down to the pub with Ford Prefect. --Woozle 21:46, 18 July 2007 (EDT)