This occurs when you find that your boyfriend/girlfriend's roommate is a far better match for you. This leads you to think of a plan to "switch" roomates. However, this is not an easy task. People during the middle ages were locked up for even thinking about it.

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)

The time in a man's life when his balls get tired and start hanging lower than the rest of the penis.

The switch is an interesting sexual move usually performed by two males on an unsuspecting female. The two males state a time and location.

The first male (let's call him Mike) is to bring his girlfriend or wife to the given location at the given time. They proceed to have sex doggy style.

Mike's friend (Jimmy) silently enters the location and strips down. After a predetermined signal is given Mike and Jimmy switch positions so that Jimmy is now fucking Mike's girlfriend. This action is so fast that Mike's girlfriend does not realize who is now fucking her. Usually followed by a Manhattan Divorce.

When hooking up with a girl, the guy leaves the room and another guy comes in and takes his place, without the girl ever noticing.

In regions which require seasonal clothing, "the switch" is the act of switching out one season's clothes for another. It's very important not to do "the switch" too early or all the clothes you need will be in the basement, leaving you freezing or sweltering.