Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

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