Dictionary.net

a name borrowed from the West Indian freebooters of the sixteenth and seventeenth centuries and applied to associations originating in the United States for the ostensible purpose of freeing Cuba and other West Indian islands or Central American districts from European control. The acquisition of Texas was a successful filibustering expedition. In 1850 Lopez, a Cuban, Governor Quitman, of Mississippi, and others, were arrested for violating the neutrality law of 1818, by a proposed filibustering expedition against Cuba. They were afterward released. In 1855 General William Walker, with a California company, sailed on a filibustering expedition against Nicaragua. He took possession of the country, was elected President and was recognized by the American Minister. He surrendered to the United States, but organized another expedition in 1860. He was captured and shot by the President of Honduras. This ended filibustering. The term " filibuster " as used in respect to parliamentary proceedings, in the sense of engaging in dilatory tactics, is no doubt derived from this, in the meaning of carrying on irregular warfare.