undergrounder

noun3

1. •
   A person who dwells underground.
2. •
   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. — 1985
3. •
   An underground publication or movie.

   • The excess that is so noticeable in Stevens's brawl is absent in the least serious undergrounder, […] — 1957