Following what is going on in someone's life by watching their status messages on Instant Messengers such as MSN, and their updates to their social networking profiles on websites like Facebook or MySpace. Akin to stalking in the real world, but usually done to people who are your friends that would normally share this information with you, however you're just too busy to keep up conversation with them.

Banging someone while you're taken.

when a man is trying to go after someone who is takin'.

1. The act of hitting on chicks when you are black-out drunk in hopes of hooking up with them. The act is usually committed by a person who is know to frequently do this, a creeper.
2. The act of macking on extremely drunk chicks when you are still sober, also a common act done by creepers.

The act of sleeping with another person while already going out with/being married to someone

to be creepy or stalk someone inappropriately.

A more commonly used phrase for the Act of Backyard Hopping or fence hopping