WordNet sense 1 (`Johnny' was applied as a nickname for Confederate soldiers by the Federal soldiers in the American Civil War; `greyback' derived from their grey Confederate uniforms):

Johnny, Reb, rebel, greyback, Johnny Reb

WordNet sense 2 (someone who exhibits great independence in thought and action):

maverick

WordNet sense 3 (a person who takes part in an armed rebellion against the constituted authority (especially in the hope of improving conditions)):

insurgent, insurrectionist, freedom fighter

WordNet sense 4 (break with established customs):

renegade

WordNet sense 5 (take part in a rebellion; renounce a former allegiance):

arise, rise, rise up

WordNet sense 6 (in or characteristic of a region of the United States south of (approximately) the Mason-Dixon line):

southern