The Collaborative International Dictionary of English v.0.48:

Pose \Pose\, v. t. [imp. & p. p. Posed; p. pr. & vb. n.
   Posing.] [F. poser to place, to put, L. pausare to pause,
   in LL. also, to place, put, fr. L. pausa a pause, Gr. ?, fr.
   ? to make to cease, prob. akin to E. few. In compounds, this
   word appears corresponding to L. ponere to put, place, the
   substitution in French having been probably due to confusion
   of this word with L. positio position, fr. ponere. See Few,
   and cf. Appose, Dispose, Oppose, Pause, Repose,
   Position.]
   To place in an attitude or fixed position, for the sake of
   effect; to arrange the posture and drapery of (a person) in a
   studied manner; as, to pose a model for a picture; to pose a
   sitter for a portrait.
   [1913 Webster]

WordNet (r) 3.0 (2006):

posing
    n 1: (photography) the act of assuming a certain position (as
         for a photograph or portrait); "he wanted his portrait
         painted but couldn't spare time for the sitting" [syn:
         sitting, posing]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "posing":
   acting, affectation, aping, appearance, attitudinarianism,
   attitudinizing, bluff, bluffing, characterization, cheating, color,
   coloring, deception, delusion, disguise, dissemblance, dissembling,
   dissimulation, dumb show, embodiment, enacting, enactment, facade,
   face, fakery, faking, false air, false front, false show, falsity,
   feigning, feint, four-flushing, fraud, front, gilt, gloss, humbug,
   humbuggery, imitation, impersonation, imposture, incarnation,
   masquerade, meretriciousness, mimesis, mimicking, mimicry, miming,
   ostentation, outward show, pantomime, pantomiming, peacockery,
   peacockishness, performance, performing, personation,
   personification, playacting, playing, portrayal, pose, posture,
   posturing, pretense, pretension, pretext, representation, seeming,
   semblance, sham, show, simulacrum, simulation, speciousness,
   varnish, window dressing