An Acronym with several meanings:

Role Playing Game:
A category of games in which players asume and act out roles.

Report Generation Language (see CategoryProgrammingLanguages):
A ProgrammingLanguage common on miniframes and MainFrames such as the IBM AS/400. Also seen as RPG II, RPGIII, RPGIV.

Rocket Propelled Grenade:
As seen in some games: a weapon fired from a rocket launcher.