Source : Webster's Revised Unabridged Dictionary (1913)

Scentless \Scent"less\, a.
   Having no scent.

         The scentless and the scented rose.      --Cowper.

Source : WordNet®

scentless
     adj 1: lacking the sense of smell [ant: {scented}]
     2: emitting or holding no odor; "scentless wisps of straw"; "a
        scentless stretch of rocky ground"