Moxa \Mox"a\, n. [A corruption of Japan. mogusa (pronounced mongsa), an escharotic made from the plant yomigi: cf. F. moxa.] 1. (Med.) A soft woolly mass prepared from the young leaves of {Artemisia Chinensis}, and used as a cautery by burning it on the skin; hence, any substance used in a like manner, as cotton impregnated with niter, amadou. [1913 Webster] 2. (Bot.) A plant from which this substance is obtained, esp. {Artemisia Chinensis}, and {Artemisia moxa}. [1913 Webster]