jackknife(redirected from Jack knife)
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Related to Jack knife: Swiss Army knife
1. A large clasp knife.
2. Sports A dive in the pike position, in which the diver straightens out to enter the water hands first.
v. jack·knifed, jack·knif·ing, jack·knifes
1. To fold or double (something or oneself) like a jackknife.
2. To cut or stab with a jackknife.
1. To bend or fold up like a jackknife: A truck that had jackknifed was blocking the road.
2. To form a 90° angle.
n, pl -knives
1. (Tools) a knife with the blade pivoted to fold into a recess in the handle
2. (Swimming, Water Sports & Surfing) a former name for a type of dive in which the diver bends at the waist in midair, with the legs straight and the hands touching the feet, finally straightening out and entering the water headfirst: forward pike dive
3. (Automotive Engineering) (of an articulated lorry) to go out of control in such a way that the trailer swings round at an angle to the cab
4. (Swimming, Water Sports & Surfing) to make a jackknife dive
n., pl. -knives, n.
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.v.i.
3. to bend over from or at the middle; double over like a jackknife.
4. (of a trailer truck) to have the cab and trailer swivel at the linkage until they form a Vshape, as the result of an abrupt stop or accident.
5. (in diving) to perform a jackknife.v.t.
6. to cause to jackknife.
7. to cut with a jackknife.
Past participle: jackknifed
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|Noun||1.||jackknife - a large knife with one or more folding blades|
|2.||jackknife - a dive in which the diver bends to touch the ankles before straightening out|
|Verb||1.||jackknife - dive into the water bending the body at the waist at a right angle, like a jackknife|
dive - plunge into water; "I was afraid to dive from the board into the pool"