Filibuster
2 of the 7 encyclopedias on this shelf carry an entry for Filibuster. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
fil'i-bus-ter, a member of a lawless band. The word is Dutch, signifying a freebooter, rover, or buccaneer. Now that the days of piracy are practically over, the term is applied to a member of an armed party that interferes in the affairs of a foreign country for the purpose of producing a revolution. Such an expedition was conducted by Lopez from New Orleans against Cuba in 1851. In 1853 William Walker of California conducted a filibustering expedition against the state of Sonora, and in 1855 a second expedition against Nicaragua. Both of these leaders, it may be said in passing, were arrested and executed. In case of arrest and imprisonment a filibuster has no claim on his home government for protection. In 1895 Dr. Jamieson organized a raid against the Boer government in South Africa. Garibaldi's various attacks on the Papal States were in reality filibustering expeditions, although the final success of the cause which he espoused has given him the rank of a patriot and revolutionist, rather than a filibuster. In parliamentary usage, a movement organized by the opposition party or a faction to obstruct the course of legislation is called a filibuster.
Collier's New Encyclopedia (1921)
a sea-rover; a pirate; a corsair; a freebooter, or buccaneer; sometimes applied to any military adventurer who undertakes an expedition against a territory, unauthorized by law or the exigencies of war. The term filibuster, now used in any country where the English language is spoken, was first applied in New Orleans to certain adventurers who, after the termination of the war between this country and Mexico, exerted themselves with setting on foot within the United States military expeditions designed to operate in the Spanish-American countries to the S. of The pretended object of these expeus. ditions was the emancipation of those countries from tyranny, foreign or domestic, and the introduction of democratic institutions after the model of the United States. The most noted expedition of this sort was that led by Walker against Nicaragua in 1855. See WALKER, WILLIAM.