When the accelerator is pushed so far it cant move any more- in some cars it hits a metal bar, or the end of the footwell (which is hopefully made of metal).

Hence the term pedal to the metal. Obviously if you have the accelerator all the way fowards youre gonna be gathering speed...or going fairly fast.

When one pushes the gas pedal to the floor, making the vehicle burst to its highest possible speed. Generally done on straightaways or during drag races, accompanied by a burnout.

1. when a vehicle is going as fast as it can
2. something you say when you want someone to go faster in a car, see hammer down.

for Brazilians (cariocas specially and often) - to shoot everything that moves as an order to kill