1. To be demoted to a lower league, as in:

Manchester United will surely go down next season or there is no God.

2. (Of computer systems) To fail to the point of being unusable without repair.

Gosh darn it. This IIS webserver goes down more often than a fi' dollar ho.

3. (Oxbridge terminology /msg me if you know of wider usage) To leave university at the end of a term to go home. This is different from being sent down, which is a Bad Thing indeed.

You will be expected to hand your key in at the porter's lodge before you go down or you will incur a hefty surcharge on your battels, which funds our fondness for port.