Typically used in the world of sport and videogames.
If you're booming someone, you're absolutely destroying them.

The act of being on psychadelic mushrooms.

1. A very gay way of partying

2. An interesting, and very strange way of masturbating

3. Getting High

4. Something better than an orgasm

The act of shitting so hard that you enter another spiritual dimension, similar to tripping on mushrooms

something that is out of this world amazing, even orgasmic

In Real-Time Strategy games, the practice of building up a massive attacking force without actually attacking while building up. The resulting huge army is then hurled against an enemy with the intention of destroying them in one fell swoop. However, this tactic invariably fails against experienced players, since an area-attack weapon (like an Onager) can often flatten the whole invading army at a stroke. This then leaves the booming player open to unopposed retaliatory attacks.

To ditch your friends or leave secretly and unannounced.