The Collaborative International Dictionary of English v.0.48:

Affectation \Af`fec*ta"tion\, n. [L. affectatio: cf. F.
   affectation.]
   1. An attempt to assume or exhibit what is not natural or
      real; false display; artificial show. "An affectation of
      contempt." --Macaulay.
      [1913 Webster]

            Affectation is an awkward and forced imitation of
            what should be genuine and easy, wanting the beauty
            that accompanies what is natural what is natural.
                                                  --Locke.
      [1913 Webster]

   2. A striving after. [Obs.] --Bp. Pearson.
      [1913 Webster]

   3. Fondness; affection. [Obs.] --Hooker.
      [1913 Webster]

WordNet (r) 3.0 (2006):

affectation
    n 1: a deliberate pretense or exaggerated display [syn:
         affectation, mannerism, pose, affectedness]

Moby Thesaurus II by Grady Ward, 1.0:

196 Moby Thesaurus words for "affectation":
   Barnumism, Gongorism, act, acting, action, actions, activity, acts,
   address, affectedness, air, airs, appearance, artfulness, artifice,
   artificiality, attitudinizing, bearing, bedizenment, behavior,
   behavior pattern, behavioral norm, behavioral science, big talk,
   bluff, bluffing, carriage, cheating, color, coloring,
   command of language, comportment, conduct, convolution,
   culture pattern, custom, deception, delusion, demeanor, deportment,
   disguise, dissemblance, dissembling, dissimulation, doing, doings,
   euphemism, euphuism, exaggeration, expression of ideas, facade,
   face, fakery, faking, false air, false front, false show, falsity,
   fashion, feeling for words, feigning, feint, flashiness,
   flatulence, flatulency, folkway, form of speech, four-flushing,
   fraud, front, fulsomeness, garishness, gaudiness, gestures, gilt,
   gloss, goings-on, grace of expression, grandiloquence,
   grandioseness, grandiosity, guise, high-flown diction, humbug,
   humbuggery, hyperelegance, imposture, inflatedness, inflation,
   insincerity, lexiphanicism, literary style, loftiness, lugs,
   luridness, magniloquence, maintien, manner, manner of speaking,
   manneredness, mannerism, manners, masquerade, mere rhetoric,
   meretriciousness, method, methodology, methods, mien, mode,
   mode of expression, modus vivendi, motions, movements, moves,
   observable behavior, orotundity, ostentation,
   ostentatious complexity, outward show, overelaboration,
   overelegance, overniceness, overrefinement, pattern, peculiarity,
   personal style, platitudinous ponderosity, playacting, poise,
   polysyllabic profundity, pomposity, pompous prolixity, pompousness,
   pontification, port, pose, posing, posture, posturing, practice,
   praxis, preciosity, preciousness, presence, pretense, pretension,
   pretentiousness, pretext, procedure, proceeding, prose run mad,
   purism, representation, rhetoric, rhetoricalness, seeming,
   semblance, sensationalism, sense of language, sententiousness,
   sham, show, showiness, simulacrum, simulation, social science,
   speciousness, stiltedness, strain, style, stylistic analysis,
   stylistics, swelling utterance, swollen phrase, swollenness,
   tactics, tall talk, the grand style, the plain style, the sublime,
   tone, tortuosity, tortuousness, trick, tumidity, tumidness,
   turgescence, turgidity, unnaturalness, varnish, vein, way,
   way of life, ways, window dressing