The Collaborative International Dictionary of English v.0.48:

Chaw \Chaw\, v. t. [imp. & p. p. Chawed; p. pr. & vb. n.
   Chawing.] [See Chew.]
   1. To grind with the teeth; to masticate, as food in eating;
      to chew, as the cud; to champ, as the bit.
      [1913 Webster]

            The trampling steed, with gold and purple trapped,
            Chawing the foamy bit, there fiercely stood.
                                                  --Surrey.
      [1913 Webster]

   2. To ruminate in thought; to consider; to keep the mind
      working upon; to brood over. --Dryden.
      [1913 Webster]

   Note: A word formerly in good use, but now regarded as
         vulgar.
         [1913 Webster]