What, lockeD doesnt know about locking?? 
I believe its when you downshift from 4th to 3rd gear or 3rd to 2nd. Basically its the opposite of what clutch kicking is, instead of the flywheel spinning to fast than being slowed down from connecting with the driveshaft, the driveshaft is spinning to fast and connects with the flywheel. Must be done on surfaces with little traction or you’ll likely snap your U-joints or yokeslip
Speeding into a corner and then downshifting from third to second without heel-toe shifting, or fourth to third gear for higher speed drifts, causes the drive train to lock, car to slow, and the engine rpm to peak. The quick shift without rev matching causes the drive wheels to momentarily lock initiating the drift and the high engine rpm gives you the horsepower and torque needed to smoke the tires.
Drift Sequence:
1.Gas all the way in third gear
2.Brake
3.Steer
4.Let clutch go without using heel-toe technique.
5.Rear wheels will suddenly lock
6.Then slide
7.Countersteer
8.After car is facing corner exit, gently give the car gas – how hard you step on the gas depends how much you are countersteering and sliding.
The shift lock drifting technique can be damaging to engine rods because the ECU is unable to rev limit when the rear wheels are spinning faster than the engine’s fly wheel. Drivers who downshift too early are sometimes called “Rod Stretchers.”
Since shift lock drifting can damage a drift car, it is recommended to practice on a wet surface or snow if possible when learning how to drift using this technique.