Green’s Dictionary of Slang

1. (US) to crash.

1918		J.N. Hall High Adventure 59: ‘[P]an-caking is n’t too bad. Not in a Blériot. Just like falling through a shingle roof. Can’t hurt yourself much’.
1919		C.E. Piesbergen Overseas with an Aero Squadron 70: John J. was intended to be a flyer, but something went wrong and John pancaked.

2. to flatten.

1943		Smith & Carnes American Guerrilla 192: The men at his heels [...] dropped sprawling in their tracks, pancaking their bodies on the ground before more bullets should streak from the darkness .
1953		W. Eyster Far from the Customary Skies 324: Oklahoma was trying to pancake a white hat so it would stay on the back of his head.
2005		J. Stahl I, Fatty 157: My gratitude over not getting pancaked in the quake.

3. (US) to knock down and run over.

1977		J. Sayles Union Dues (1978) 54: They go a couple of tons, no suspension, they run over your toes it’s pancake time, right?
2001		J. Stahl Plainclothes Naked (2002) 123: Some sick fuckos pancaked the sky-pilot and left him for dead.

4. (US black/teen) to lower the body of an automobile.

1980

E. Folb Runnin’ Down Some Lines 249: pancake Drop the body of a car-first the back end, then the front end, then a reversal of the process.