The Collaborative International Dictionary of English v.0.48:
Peritonitis \Per`i*to*ni"tis\, n. [NL. See Peritoneum, and -itis.] (Med.) Inflammation of the peritoneum. [1913 Webster]WordNet (r) 3.0 (2006):
peritonitis n 1: inflammation of the peritoneum [syn: peritonitis, peritoneal inflammation]