The Collaborative International Dictionary of English v.0.48:

Theatrical \The*at"ric*al\, a. [L. theatricus, Gr. ?.]
   Of or pertaining to a theater, or to the scenic
   representations; resembling the manner of dramatic
   performers; histrionic; hence, artificial; as, theatrical
   performances; theatrical gestures. -- The*at`ri*cal"i*ty,
   n. -- The*at"ric*al*ly, adv.
   [1913 Webster]

         No meretricious aid whatever has been called in -- no
         trick, no illusion of the eye, nothing theatrical. --R.
                                                  Jefferies.
   [1913 Webster]

WordNet (r) 3.0 (2006):

theatrical
    adj 1: of or relating to the theater
    2: suited to or characteristic of the stage or theater; "a
       theatrical pose"; "one of the most theatrical figures in
       public life" [ant: untheatrical]
    n 1: a performance of a play [syn: theatrical performance,
         theatrical, representation, histrionics]