Source : Webster's Revised Unabridged Dictionary (1913)

Deceitful \De*ceit"ful\, a.
   Full of, or characterized by, deceit; serving to mislead or
   insnare; trickish; fraudulent; cheating; insincere.

         Harboring foul deceitful thoughts.       --Shak.

Source : WordNet®

deceitful
     adj 1: intended to deceive; "deceitful advertising"; "fallacious
            testimony"; "smooth, shining, and deceitful as thin
            ice" - S.T.Coleridge; "a fraudulent scheme to escape
            paying taxes" [syn: {fallacious}, {fraudulent}]
     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}, {double-dealing}, {duplicitous}, {Janus-faced},
         {two-faced}, {double-faced}, {double-tongued}]