The Collaborative International Dictionary of English v.0.48:

Rabidity \Ra*bid"i*ty\ (r[.a]*b[i^]d"[i^]*t[y^]), n.
   Rabidness; furiousness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rabidity
    n 1: unrestrained excitement or enthusiasm; "poetry is a sort of
         divine madness" [syn: madness, rabidity, rabidness]