For those of you who play Real Time Strategy games, to rush is to, early on in a scenario, build a large, mobile army and attack an opponent, hopefully catching them unaware while they are still building up their infrastructure.

This term is increasingly used in real business situations, both for people internally planning to get support for their idea "let's do an email rush before the report is released," and externally, "it is not enough to be an early mover. We have to do a tank rush to dominate the store shelves."

This is typically an all or nothing strategy, that if fails, leaves the attacker in a vulnerable situation.