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):

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

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "acridity":
   acerbity, acidity, acidness, acidulousness, acridness, acrimony,
   acuity, acumination, acuteness, asperity, astringence, astringency,
   bite, bitingness, bitter pill, bitterness, causticity, causticness,
   corrosiveness, cuttingness, edge, fierceness, gall,
   gall and wormwood, grip, harshness, incisiveness, keenness,
   mordacity, mordancy, mucronation, piercingness, piquancy,
   poignancy, point, pointedness, prickliness, pungency, rigor,
   roughness, severity, sharpness, sourness, spinosity, stabbingness,
   sting, stridency, stringency, tartness, teeth, thorniness,
   trenchancy, vehemence, violence, virulence