Wordnet 3.0
ADJECTIVE (2)
1. 
 lacking the sense of smell; 
2. 
 emitting or holding no odor; 
- Example: "scentless wisps of straw"- Example: "a scentless stretch of rocky ground"
The Collaborative International Dictionary of English v.0.48:
Scentless \Scent"less\, a.
   Having no scent.
   [1913 Webster]
         The scentless and the scented rose.      --Cowper.
   [1913 Webster]
WordNet (r) 3.0 (2006):
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"