Black″–jack′, n. 1. (Min.) A name given by English miners to sphalerite, or zinc blende; — called also false galena. See Blende.
2. Caramel or burnt sugar, used to color wines, spirits, ground coffee, etc.
3. A large leather vessel for beer, etc.
4. (Bot.) The Quercus nigra, or barren oak.
5. The ensign of a pirate.