Ringworm \Ring"worm"\, n. (Med.)
A contagious affection of the skin due to the presence of a
vegetable parasite, and forming ring-shaped discolored
patches covered with vesicles or powdery scales. It occurs
either on the body, the face, or the scalp. Different
varieties are distinguished as {Tinea circinata}, {Tinea
tonsurans}, etc., but all are caused by the same parasite (a
species of {Trichophyton}).
[1913 Webster]