The Collaborative International Dictionary of English v.0.48:

Aridity \A*rid"i*ty\, n.; pl. Aridities. [L. ariditas, fr.
   aridus.]
   1. The state or quality of being arid or without moisture;
      dryness.
      [1913 Webster]

   2. Fig.: Want of interest of feeling; insensibility; dryness
      of style or feeling; spiritual drought. --Norris.
      [1913 Webster]