The Collaborative International Dictionary of English v.0.48:

Odorant \O"dor*ant\, a. [L. odorans, -antis, p. pr.]
   Yielding odors; fragrant. --Holland.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

odorant \o"dor*ant\, n.
   An odorous substance; especially, a substance with a strong
   odor added to a dangerous substance, such as natural gas, to
   provide an easy detection method and a warning; as, ethyl
   mercaptan is used as an odorant in natural gas and propane to
   facilitate detection of leaks.
   [PJC]