fibrositis n inflammation of white fibrous tissues (especially muscle sheaths) Usage(s) Symptoms most often resemble those of fibrositis and the two are often confused. So did Australia, shortly afterward, when tissue-swelling fibrositis crippled its sports hero, Cricketer Don Bradman. The elephants of the Bertram Mills circus in London were in a painful fix with fibrositisthickening of the trunk muscles.