What is the dangerous phenomenon known as 'jackknifing' (makazanje / sklapanje skupa vozila) in an articulated tractor-semitrailer?

1. The tractor unit's drive wheels lose lateral grip, causing the tractor to rotate rapidly relative to the semitrailer until the cab folds into the side of the trailer like a pocketknife
2. The trailer disconnects from the fifth wheel kingpin completely and rolls into the ditch
3. The engine stalls and restarts in reverse
4. The cargo rolls off the side of the flatbed