to engage in sexual interactions with your best friends girlfriend. Could be anything from kissing to sex. in order to jake it, you can't have any emotions and just can't care about the consequence.
Friend 1- "yo i'm gonna be alone with ben's girlfriend what should we do!"
Friend 2- "jake it!"
Friend 1- "you mean fuck her and not care about if ben finds out?!"
Friend 2- "yeaaah!"