The Collaborative International Dictionary of English v.0.48:

Congratulation \Con*grat`u*la"tion\, n. [L. congratulatio: cf.
   F. congratulation.]
   The act of congratulating; an expression of sympathetic
   pleasure.
   [1913 Webster]

         With infinite congratulations for our safe arrival.
                                                  --Dr. J.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

congratulation
    n 1: the act of acknowledging that someone has an occasion for
         celebration [syn: congratulation, felicitation]
    2: (usually plural) an expression of pleasure at the success or
       good fortune of another; "I sent them my sincere
       congratulations on their marriage" [syn: congratulation,
       felicitation]

The Devil's Dictionary (1881-1906):

CONGRATULATION, n.  The civility of envy.