The Collaborative International Dictionary of English v.0.48:

Jounce \Jounce\ (jouns), v. t. & i. [imp. & p. p. Jounced
   (jounst); p. pr. & vb. n. Jouncing (joun"s[i^]ng).] [Cf.
   Jaunce.]
   To jolt; to shake, especially by rough riding or by driving
   over obstructions.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jounce \Jounce\, n.
   A jolt; a shake; a hard trot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

jounce
    n 1: a sudden jarring impact; "the door closed with a jolt";
         "all the jars and jolts were smoothed out by the shock
         absorbers" [syn: jolt, jar, jounce, shock]
    v 1: move up and down repeatedly [syn: bounce, jounce]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "jounce":
   bob, bobble, bounce, bump, chatter, collision, concussion, didder,
   falter, have an ague, hustle, impingement, jactitate, jar, jog,
   joggle, jolt, jostle, jump, percussion, quake, quaver, quiver,
   shake, shiver, shock, shudder, tremble, twitter, vibrate, wallop,
   wobble