The Collaborative International Dictionary of English v.0.48:

Mannered \Man"nered\, a.
   1. Having a certain way, esp. a polite way, of carrying and
      conducting one's self; as, a well-mannered child.
      [1913 Webster]

            Give her princely training, that she may be
            Mannered as she is born.              --Shak.
      [1913 Webster]

   2. Affected with mannerism; marked by excess of some
      characteristic peculiarity.
      [1913 Webster]

            His style is in some degree mannered and confined.
                                                  --Hazlitt.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mannered
    adj 1: having unnatural mannerisms; "brief, mannered and
           unlifelike idiom"

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "mannered":
   Gongoresque, Gongoristic, Marinistic, affected, allusive,
   artificial, behaved, behavioral, behaviored, behaviorist,
   behavioristic, conscious, contrived, demeanored, elaborate,
   elaborated, euphuistic, figurative, figured, flowery, high-hat,
   highfalutin, histrionic, hoity-toity, hyperelegant, hypocritical,
   insincere, la-di-da, maniere, metaphorical, ornamented, overacted,
   overdone, overelaborate, overelegant, overnice, overrefined,
   pompous, posed, precieuse, precieux, precious, pretentious, pseudo,
   referential, stagy, stiff, stilted, studied, theatrical,
   trolatitious, tropological, unnatural