Source : Webster's Revised Unabridged Dictionary (1913)

Guileless \Guile"less\, a.
   Free from guile; artless. -- {Guile"less*ly}, adv.
   {Guile"less*ness}, n.

Source : WordNet®

guileless
     adj 1: free from guile; "his answer was simple and honest" [syn: {honest}]
     2: free of deceit [syn: {transparent}]