Downdraft (adjective) refers to the circulation of the air inside a kiln while it is firing. In a downdraft kiln, the air moves from a burner or firebox at the base of the kiln upward into the stack area, then swirls back downward to exhaust through a chimney opening at the base of the kiln.
Downdraft (noun) is also often used by potters as a shortened form of "downdraft kiln".
I've got a glaze load to set into the downdraft kiln tomorrow.(adjective)
I'll be doing back-to-back firings in the downdraft all week. (noun)