The Collaborative International Dictionary of English v.0.48:

Jerk \Jerk\, n.
   [1913 Webster]
   1. A short, sudden pull, thrust, push, twitch, jolt, shake,
      or similar motion.
      [1913 Webster]

            His jade gave him a jerk.             --B. Jonson.
      [1913 Webster]

   2. A sudden start or spring.
      [1913 Webster]

            Lobsters . . . swim backwards by jerks or springs.
                                                  --Grew.
      [1913 Webster]

   3. A foolish, stupid, or otherwise contemptible person.
      [Slang]

   Syn: jerkoff.
        [PJC]

   4. (Sport) The lifting of a weight, in a single rapid motion,
      from shoulder height until the arms are outstretched above
      the head; distinguished from press in that the motion in
      a jerk is more rapid, and the body may be moved under the
      weight to assist completion of the movement; as, a clean
      and jerk of two hundred pounds.
      [PJC]

   2. Calisthenic exercises, such as push-ups or deep knee
      bends; also called physical jerks. [British]
      [PJC]