Definitions

1. noun

the act of a semi-trailer or a trailer truck’s trailer swinging outward from the towing vehicle, often causing an accident

“The jackknifing of the semi-truck on the icy road caused a major traffic congestion.”

2. verb

to cause a semi-trailer or a trailer truck’s trailer to swing outward from the towing vehicle, often causing an accident

“The driver lost control and started jackknifing the trailer down the mountain.”