The act of fucking people on the side while in a horrible long distance relationship. Since people cannot cope with long distance relationships they need the additional sexual satisfaction of having sex with other people. The long distance partner cannot possibly satisfy the other through the use of phone or web sex, so additional partners are required to quench this desire.
D: So how's your boyfriend in Vancouver doing?
J: So fucking bad, thank god I'm sidefucking.
D: Oh I know what you mean, sidefucking is essential. Like when I was dating that chick in Utah.
A stealth form of male masturbation performed while wearing pants, typically in a semi-public setting such as a movie theater or while driving. In order to sidehack a man must first position his penis along his inner thigh. He will them stimulate the penis by rubbing or stroking his inside thigh through his pants.
Synonym of "sidechick" but for a girl. A guy who a slut is currently being boned by along with a number of other guys, or sidedicks. A guy with whom a girl regularly cheats on her boyfriend with.