The Collaborative International Dictionary of English v.0.48:

jitters \jitters\ n.
   an uneasy state; nervousness; as, the prospect of being
   drafted gave him a bad case of the jitters.

   Syn: nervousness, nerves, screaming meemies.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

jitters
    n 1: extreme nervousness [syn: jitters, heebie-jeebies,
         screaming meemies]