Source : Webster's Revised Unabridged Dictionary (1913)

Black-jack \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. [Obs.]

   4. (Bot.) The {Quercus nigra}, or barren oak.

   5. The ensign of a pirate.

Source : WordNet®

Quercus nigra
     n : relatively tall deciduous water oak of southeastern United
         States often cultivated as a shade tree; thrives in wet
         soil [syn: {water oak}, {possum oak}]