subversive organization

any organization which engages in or advocates, abets, advises, or teachers, or a purpose of which is to engage in or advocate, abet, advise, or teach activities intended to overthrow, destroy or alter, or to assist in the overthrow, destruction or alteration of, the constitutional form of the government of the United States, or of the state of New Hampshire, or of any political subdivision of either of them, by force, or violence.

Defined by the Supreme Court in Sweezy v. State of New Hampshire C Wyman, 354 U.S. 234 (1957).

See also 380 U.S. 479.