The Collaborative International Dictionary of English v.0.48:

Repercussion \Re`per*cus"sion\ (-k?sh"?n), n. [L. repercussio:
   cf. F. r['e]percussion.]
   1. The act of driving back, or the state of being driven
      back; reflection; reverberation; as, the repercussion of
      sound.
      [1913 Webster]

            Ever echoing back in endless repercussion. --Hare.
      [1913 Webster]

   2. (Mus.) Rapid reiteration of the same sound.
      [1913 Webster]

   3. (Med.) The subsidence of a tumor or eruption by the action
      of a repellent. --Dunglison.
      [1913 Webster]

   4. (Obstetrics) In a vaginal examination, the act of
      imparting through the uterine wall with the finger a shock
      to the fetus, so that it bounds upward, and falls back
      again against the examining finger.
      [1913 Webster]

WordNet (r) 3.0 (2006):

repercussion
    n 1: a remote or indirect consequence of some action; "his
         declaration had unforeseen repercussions"; "reverberations
         of the market crash were felt years later" [syn:
         repercussion, reverberation]
    2: a movement back from an impact [syn: recoil,
       repercussion, rebound, backlash]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "repercussion":
   aftermath, antagonism, antipathy, backfire, backlash, backlashing,
   backwash, boomerang, bounce, bound, cantando, carom, clashing,
   clout, collision, concussion, conflict, confutation, consequence,
   contradiction, contraposition, contrariety, contrecoup,
   counteraction, counterposition, counterworking, crankiness,
   crotchetiness, crunch, demilegato, dissent, echo, effect,
   execution, expression, fallout, fingering, force, friction,
   glissando, impact, impress, impression, imprint, interference,
   intonation, kick, kickback, legato, mark, mezzo staccato,
   music-making, nonconformity, opposition, opposure, oppugnance,
   oppugnancy, outcome, parlando, percussion, performance,
   perverseness, pianism, pizzicato, print, reaction, rebound, rebuff,
   recalcitrance, recalcitration, recoil, reflex, rendering,
   rendition, renitency, repugnance, repulse, resilience, resistance,
   response, result, reverberation, revolt, ricochet, rubato, shock,
   slur, smash, spiccato, spring, staccato, swimming upstream, touch,
   upshot