The Collaborative International Dictionary of English v.0.48:

Complacent \Com*pla"cent\, a. [L. complacens very pleasing, p.
   pr. of complacere; com- + placere to please: cf. F.
   complaisant. See Please and cf. Complaisant.]
   Self-satisfied; contented; kindly; as, a complacent temper; a
   complacent smile.
   [1913 Webster]

         They look up with a sort of complacent awe . . . to
         kings.                                   --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

complacent
    adj 1: contented to a fault with oneself or one's actions; "he
           had become complacent after years of success"; "his self-
           satisfied dignity" [syn: complacent, self-satisfied,
           self-complacent]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "complacent":
   bovine, consequential, narcissan, narcissine, narcissistic,
   narcistic, overproud, overweening, self-admiring, self-approving,
   self-assuming, self-complacent, self-congratulating,
   self-congratulatory, self-content, self-contented, self-delighting,
   self-endeared, self-esteeming, self-gratulating, self-gratulatory,
   self-important, self-loving, self-respecting, self-satisfied,
   self-sufficient, smug, vain, vainglorious