Source : Webster's Revised Unabridged Dictionary (1913)

Pneumonitis \Pneu`mo*ni"tis\, n. [NL. See {Pneumo-}, and
   {-itis}.] (Med.)
   Inflammation of the lungs; pneumonia.

Source : WordNet®

pneumonitis
     n : inflammation of the lungs; caused by a virus or an allergic
         reaction