undergrounder

noun

1. An underground publication or movie.

   “1957, Manny Farber, "Underground Films", in Robert Walsh (ed.) Negative Space: Manny Farber on the movies (1998), p. 27, The excess that is so noticeable in Stevens's brawl is absent in the least serious undergrounder, […]”

   “1985, Abe Peck, Uncovering the Sixties: The Life and Times of the Underground Press, p. 51, Street people, day-trippers, and tourists pushed the paper's circulation to 117,000, the largest any community undergrounder would reach.”

2. A person who dwells underground.

   “[…] sewer people, derelicts, bag ladies, undergrounders, and Bowery bums. Whatever the cause of their illness, as in Scanners, homeless people are victims but, more importantly, a threat to be eliminated.”

3. One who is part of a secret or underground society or subculture.

   “His tactics appealed to the type of Old Bolshevik undergrounder who had little patience with theoretical hairsplitting and who looked to a firm authority to take the lead in practical work.”