noun

1. an adventurer who engages in unauthorized warfare against a country with which his own country is at peace; specif., any of the 19th-cent. U.S. adventurers who led armed expeditions into Latin American countries; freebooter
2. ☆
   1. the making of long speeches, introduction of irrelevant issues, etc. in order to obstruct the passage of a bill in the Senate
   2. a member of the Senate who uses such methods
      also filibusterer fil′i·bus′·terer

Etymology: Sp filibustero < Fr flibustier, earlier fribustier < MDu vrijbuiter, freebooter

intransitive verb

1. to engage in unauthorized warfare as a freebooter
2. ☆ to engage in a filibuster

transitive verb