The Collaborative International Dictionary of English v.0.48:

Cheval \Che*val"\, n.; pl. Chevaux. [F. See Cavalcade.]
   A horse; hence, a support or frame.
   [1913 Webster]

   Cheval glass, a mirror swinging in a frame, and large
      enough to reflect the full length figure.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cheval glass
    n 1: a full length mirror mounted in a frame in which it can be
         tilted