The equivalent of doing repetitions with weights during strength training very hard and fast but for gaming. Being able to speed through a video game completing objectives and gaining levels as fast as possible. It also applies to destroying multiple enemies in a short amount of time. Usually preceded and followed by multiple swears.
"I have being reping through Skyrim; I'm three hours in and already level 35!"
"I repped through those pussy Grunts in no time!"
"I'm fucking reping through these motherfuckers!"