heel-toe shift

The heel-toe shift is a racing technique used to downshift while braking. It's used mainly when approaching a corner at high speed, and you wanna slow down and downshift as fast as possible.

To correct another definition here, you apply brakes and depress the clutch pedal, and move the shifter into neutral. Keeping your ball-of-foot/toes on the brakes, pivot your right foot so that your heel can "blip" the throttle, immediately move the shifter down a gear, and then release the clutch pedal smoothly before the revs drop down again.