This term is used in Starcraft 2. It describes the action that a player takes when he forfeits all other unit building and starts building a fleet of Battlecruisers. A player can switch to "full taco" midgame or can have a "full taco" strategy from the start. This is a common strategy among new players, as it requires a shitload of resources to be successful. The game can end before even one Battlecruiser is built.
"I think he's going to go full taco, we should hit early."