The Collaborative International Dictionary of English v.0.48:

Rankness \Rank"ness\, n. [AS. rancness pride.]
   The condition or quality of being rank.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rankness
    n 1: the property of producing abundantly and sustaining
         vigorous and luxuriant growth; "he praised the richness of
         the soil"; "weeds lovely in their rankness" [syn:
         richness, rankness, prolificacy, fertility]
    2: the attribute of having a strong offensive smell [syn:
       malodorousness, stinkiness, foulness, rankness,
       fetidness]