Given that this is in Roleplaying Games and not 3.x/d20, I'm assuming it refers to the archetype. As such, there are a few major types.

1) Someone from a "primitive" culture, who respects their own culture, sees flaws in larger civilization, and is far more independant and capable than those "civilized" folk. This type usually shows up in Sword and Sorcery games.

2) Someone from a very advanced culture, likely with several technologies beyond that of "civilized" cultures, that is likely more nomadic or simply less urban than whatever local empire views itself as the center of the world.

3) Someone from a culture that can actually be called primitive that is in the process of abandoning it.