The Collaborative International Dictionary of English v.0.48:

Chaperon \Chap"er*on\, n. [F. chaperon. See Chape, Cape,
   Cap.]
   1. A hood; especially, an ornamental or an official hood.
      [1913 Webster]

            His head and face covered with a chaperon, out of
            which there are but two holes to look through.
                                                  --Howell.
      [1913 Webster]

   2. A device placed on the foreheads of horses which draw the
      hearse in pompous funerals.
      [1913 Webster]

   3. A matron who accompanies a young lady in public, for
      propriety, or as a guide and protector.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chaperon \Chap"er*on\, v. t. [imp. & p. p. Chaperoned; p. pr.
   & vb. n. Chaperoning.] [Cf. F. chaperonner, fr. chaperon.]
   To attend in public places as a guide and protector; to
   matronize.
   [1913 Webster]

         Fortunately Lady Bell Finley, whom I had promised to
         chaperon, sent to excuse herself.        --Hannah More.
   [1913 Webster]

WordNet (r) 3.0 (2006):

chaperon
    n 1: one who accompanies and supervises a young woman or
         gatherings of young people [syn: chaperon, chaperone]
    v 1: accompany as a chaperone [syn: chaperone, chaperon]