buntovnik

1. rebel
   Buntovnici su zauzeli gradsku većnicu. — The rebels seized the town hall.
2. (of character) rebel; nonconformist
   U pubertetu je bio pravi buntovnik. — As a teenager he was a real rebel.
   Uvek je bila buntovnik u porodici. — She was always the rebel of the family.

The feminine form is buntovnica.