Source : Webster's Revised Unabridged Dictionary (1913)

Double-faced \Dou"ble-faced`\, a.
   1. Having two faces designed for use; as, a double-faced
      hammer.

   2. Deceitful; hypocritical; treacherous. --Milton.

Source : WordNet®

double-faced
     adj 1: (of fabrics) having faces on both sides; "damask is a
            double-faced fabric"
     2: marked by deliberate deceptiveness especially by pretending
        one set of feelings and acting under the influence of
        another; "she was a deceitful scheming little thing"-
        Israel Zangwill; "a double-dealing double agent"; "a
        double-faced infernal traitor and schemer"- W.M.Thackeray
        [syn: {ambidextrous}, {deceitful}, {double-dealing}, {duplicitous},
         {Janus-faced}, {two-faced}, {double-tongued}]