The Collaborative International Dictionary of English v.0.48:

comeuppance \come`up"pance\ (k[u^]m`[u^]p"pans), n.
   An unpleasant experience a person endures, which is viewed by
   others as a just retribution for bad behavior; just deserts;
   as, the Senator took bribes for years, and finally got his
   comeuppance when he was caught in a sting operation.
   [PJC]

WordNet (r) 3.0 (2006):

comeuppance
    n 1: an outcome (good or bad) that is well deserved [syn:
         deserts, comeuppance, comeupance]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "comeuppance":
   compensation, desert, deserts, deserving, due, due reward, dues,
   just deserts, merit, merits, punishment, quittance, recompense,
   reprisal, requital, retribution, revenge, reward, rights,
   what is due, what is merited