From what I know, it's when an 18-wheeler is carrying one of those loads, any loads, as long as it's carry a load, and it's going at quite a highspeed, suddenly braking, causing the actual truck itself to brake whilst the load's momentum behind the truck forces itself in motion against the truck, causing the load
on the back to be intersecting at a
perpendicular angle with the truck. Look at this---> |_ The | is the actual truck and the _ is it's load. The truck (|) is going forward, whilst the load (_) is scraping it's tires horizontally.
A jackknife is also
responsible for causing many highway accidents, because when a truck jackknifes, it takes up all the lanes on the highways, and leaves no mercy for the vehicles in its path! Always speed up if you see a jackknife coming toward you if you cannot rapidly get off the highway.
*people driving*
Oh crap dude, that truck is in the process of a jackknife, that
piece of shit volkswagon is in our way, guess the only choice we have is to speed up, step on it.
*person in volkswagon*
*ahhhh
this is the life, *fart*, beer and hot sauce...boomheadshot.*
