Source : Webster's Revised Unabridged Dictionary (1913)

Tonsilitis \Ton`sil*i"tis\, n. [NL. See {Tonsil}, and {-itis}.]
   (Med.)
   Inflammation of the tonsil; quinsy. [Written also, and more
   usually, {tonsillitis}.]

Source : WordNet®

tonsillitis
     n : inflammation of the tonsils (especially the palatine
         tonsils)