The Collaborative International Dictionary of English v.0.48:
Synovitis \Syn`o*vi"tis\, n. [NL. See Synovia, -itis.] (Med.) Inflammation of the synovial membrane. [1913 Webster]WordNet (r) 3.0 (2006):
synovitis n 1: inflammation of the synovial membrane that lines a synovial joint; results in pain and swelling