2. Fancy Diving.
a dive in which
the diver bends in midair to touch the toes, keeping the legs straight, and then straightens out.
verb (used without object)
to bend or double over like a jackknife: The prizefighter jackknifed and fell when he was hit in the stomach.
(of a trailer truck) to have the cab and trailer swivel at the linkage until they form a V shape, as the result of an abrupt stop or accident.
(in diving) to perform a jackknife.
to move rapidly at an abrupt angle.
verb (used with object)
to cause to jackknife: The blow jackknifed the prizefighter.
to cut with a jackknife.
resembling a jackknife, as in its shape, function, or manner of opening and folding.