jackknife: Meaning and Definition of

jack•knife

1. a large pocketknife.
2. a dive in which the diver bends in midair to touch the toes, keeping the legs straight, and then straightens out.

1. to bend or double over like a jackknife: The prizefighter jackknifed and fell when he was hit in the stomach.
2. (of a trailer truck) to have the cab and trailer swivel at the linkage until they form ashape, as the result of an abrupt stop or accident.
3. (in diving) to perform a jackknife.
4. to move rapidly at an abrupt angle.

1. to cause to jackknife: The blow jackknifed the prizefighter.
2. to cut with a jackknife.

1. resembling a jackknife, as in its shape, function, or manner of opening and folding.