Reading through my 8th edition of Black's magic, I stumbled onto this definition, although it seems to have been embellished a bit!
http://cl.ly/image/2n0u2g3q3j09
Printed copy · Anthology Volume 6, page 510Printed copy from The Tender For Law Anthology, Volume 6, page 510 (printed 13 June 2014). Added by this site; not part of the Facebook export.