WordNet (r) 3.0 (2006):

black magic
    n 1: the belief in magical spells that harness occult forces or
         evil spirits to produce unnatural effects in the world
         [syn: sorcery, black magic, black art, necromancy]

The Free On-line Dictionary of Computing (19 January 2023):

black magic

    (Or "FM") A technique that works, though nobody
   really understands why.  More obscure than voodoo
   programming, which may be done by cookbook.

   Compare black art, deep magic, and magic number.

   (2001-04-30)


The Jargon File (version 4.4.7, 29 Dec 2003):

black magic
 n.

    [common] A technique that works, though nobody really understands why. More
    obscure than voodoo programming, which may be done by cookbook. Compare
    also black art, deep magic, and magic number (sense 2).