The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. To delay legislation, by dilatory motions or other
      artifices. [political cant or slang, U.S.] --Bartlett.
      [1913 Webster]