Source : Webster's Revised Unabridged Dictionary (1913)

Congratulatory \Con*grat"u*la*to*ry\, a.
   Expressive of sympathetic joy; as, a congratulatory letter.

Source : WordNet®

congratulatory
     adj : expressive of sympathetic pleasure or joy on account of
           someone's success or good fortune; "a congratulatory
           telegram"; "the usual congratulatory crowd was
           conspicuously absent"; "a gratulatory address" [syn: {gratulatory}]