To toke is the action of taking a hit of marijuana, therefor, tokin up means to have a session of smoking marijuana. You can toke on a joint, or take a bong toke, and from this comes the phrase "tokin up".\n> The three of us are tokin up before the movie tonight, so we can get our [mind right] before it starts. I prefer [bong tokes], but since we will be doing in the car, it will be easier to [toke] on a joint.\n