Black-jack — A name given by English miners to sphalerite, or zinc blende; -- called also false galena. See Blende.
Black-jack — Caramel or burnt sugar, used to color wines, spirits, ground coffee, etc.
Black-jack — A large leather vessel for beer, etc.
Black-jack — The Quercus nigra, or barren oak.
Black-jack — The ensign of a pirate.