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.
MegaLlama tried booming on me, but I wiped his whole army with one Seige Onager and then razed his TC in less than 3 minutes! MWAHAHAHAHAHA!