Source : Webster's Revised Unabridged Dictionary (1913)

Doubtless \Doubt"less\, a.
   Free from fear or suspicion. [Obs.]

         Pretty child, sleep doubtless and secure. --Shak.

Doubtless \Doubt"less\, adv.
   Undoubtedly; without doubt.

Source : WordNet®

doubtless
     adv : with certainty; "it's undoubtedly very beautiful" [syn: {undoubtedly},
            {beyond question}, {without doubt}, {beyond any doubt}]