The Filly Buster is a Washington D.C. area strip club. When Steve tried to unravel the clues of a mysterious symbol he finds on jars of peanut butter in "Black Mystery Month", Stan shows him a map that he found years ago which can only be read by the Monocle Steve recovers at the Smithsonian Peanut Museum. It is a message to find the pole that bore Old Glory. At a strip club, Stan assumes that it is a flag but Steve finds out it is actually a pole shaped cane that bore America's first stripper.
The club gets its name from the term 'filibuster' a type of parliamentary procedure. Specifically, it is a form of obstruction in a legislature or other decision-making body whereby one attempts to delay or entirely prevent a vote on a proposal by extending debate.