The Collaborative International Dictionary of English v.0.48:

Acridity \A*crid"i*ty\, Acridness \Ac"rid*ness\n.
   The quality of being acrid or pungent; irritant bitterness;
   extreme bitterness; acrimony; as, the acridity of a plant, of
   a speech.

   Syn: acridness
        [1913 Webster]

   2. having an acrid smell.

   Syn: pungency
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

acridness
    n 1: extreme bitterness; "the acridity of alkali" [syn:
         acridity, acridness]
    2: the quality of being sharply disagreeable in language or tone
       [syn: acridity, acridness]