Source : Webster's Revised Unabridged Dictionary (1913)

Filibuster \Fil"i*bus`ter\, n. [Sp. flibuster, flibustero,
   corrupted fr. E. freebooter. See {Freebooter}.]
   A lawless military adventurer, especially one in quest of
   plunder; a freebooter; -- originally applied to buccaneers
   infesting the Spanish American coasts, but introduced into
   common English to designate the followers of Lopez in his
   expedition to Cuba in 1851, and those of Walker in his
   expedition to Nicaragua, in 1855.

Filibuster \Fil"i*bus*ter\, v. i. [imp. & p. p. {Fillibustered};
   p. pr. & vb. n. {Filibustering}.]
   1. To act as a filibuster, or military freebooter.
      --Bartlett.

   2. To delay legislation, by dilatory motions or other
      artifices. [political cant or slang, U.S.] --Bartlett.

Source : WordNet®

filibuster
     n 1: a legislator who gives long speeches in an effort to delay
          or obstruct legislation that he (or she) opposes [syn: {filibusterer}]
     2: a tactic for delaying or obstructing legislation by making
        long speeches
     v : obstruct deliberately by delaying; of legislation