Source : Webster's Revised Unabridged Dictionary (1913)

Synovitis \Syn`o*vi"tis\, n. [NL. See {Synovia}, {-itis}.]
   (Med.)
   Inflammation of the synovial membrane.

Source : WordNet®

synovitis
     n : inflammation of the synovial membrane that lines a synovial
         joint; results in pain and swelling