Filibuster

a sea-rover; sometimes applied to any military adventurer who undertakes an expedition against a territory, unauthorized by law or the exigencies of war. The term filibuster 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 us. The pretended object of these expeditions was the emancipation of those countries from tyranny, and the introduction of democratic institutions after the model of the United States. Though the setting on foot of such expeditions is contrary to our neutrality laws, yet the laws were frequently evaded. The most noted expedition of this sort was that led by Walker against Nicaragua in 1856, and which resulted in Walker being shot, when he attempted to lead a second expedition into the country in 1860.