The Collaborative International Dictionary of English v.0.48:

Disafforest \Dis`af*for"est\, v. t. [imp. & p. p.
   Disafforested; p. pr. & vb. n. Disafforesting.] [Pref.
   dis- + afforest: cf. OF. desaforester.] (Eng. Law)
   To reduce from the privileges of a forest to the state of
   common ground; to exempt from forest laws.
   [1913 Webster]

         By charter 9 Henry III. many forests were
         disafforested.                           --Blackstone.
   [1913 Webster]