1. To be defeated.
2. To be ingested.
3. To be recorded or remembered.
4. When something goes down in a certain way, people react to or perceive it in this way.
5. When a computer or computer network stops working because of a problem or because it has been disconnected, it goes down.
6. When the sun goes below the horizon, it goes down.

To perform fellatio or cunnilingus on.

1. When you move to a lower level or position or from north to south, you go down or go down to that place. Go up is the opposite of go down.
2. When the cost, rate, quality, quantity, or level of something decreases, it goes down. Go up is the opposite of go down.
3. When something extends to a certain point that is farther south or at a lower elevation, it goes down to that point. Go up is the opposite of go down.