As a verb, filibuster means "to obstruct legislation by talking at great length." As a noun, it can refer to that oppositional speech. "The Senator prevented a vote on the bill by reading the dictionary from aardvark to zyzzyva."
As a parliamentary tactic, the filibuster dates back to at least the first century B.C.E. The rules of the Roman Senate required that all business must be completed by nightfall, and, on more than one occasion, the senator Cato the Younger spoke until dark to delay a vote. In the Parliament of the United Kingdom, a minister may "talk out" a bill, but his speech must pertain to the bill. In the United States, by contrast, a Senator may forestall action on a bill by speaking on any topic.