The Collaborative International Dictionary of English v.0.48:

Olfaction \Ol*fac"tion\, n. [See Olfactory.] (Physiol.)
   The sense by which the impressions made on the olfactory
   organs by the odorous particles in the atmosphere are
   perceived.
   [1913 Webster]

WordNet (r) 3.0 (2006):

olfaction
    n 1: the faculty that enables us to distinguish scents [syn:
         smell, sense of smell, olfaction, olfactory
         modality]