The Collaborative International Dictionary of English v.0.48:

degarnish \de*gar"nish\, v. t. [imp. & p. p. degarnished; p.
   pr. & vb. n. degarnishing.] [F. d['e]garnir; pref. d['e]-,
   des- (L. dis-) + garnir to furnish. See Garnish, and cf.
   Disgarnish.]
   1. To strip or deprive of entirely, as of furniture,
      ornaments, etc.; to disgarnish; as, to degarnish a house,
      etc. [R.]
      [1913 Webster]

   2. To deprive of a garrison, or of troops necessary for
      defense; as, to degarnish a city or fort. [R.]
      --Washington.
      [1913 Webster]