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.

2. (Bot.) A plant from which this substance is obtained, esp. Artemisia Chinensis, and A. moxa.

Source: Webster's Revised Unabridged Dictionary (1913)