scandalum magnatum

from The Collaborative International Dictionary of English v.0.48

Scandalum magnatum \Scan"da*lum mag*na"tum`\ [L., scandal of
   magnates.] (Law)
   A defamatory speech or writing published to the injury of a
   person of dignity; -- usually abbreviated scan. mag.
   [1913 Webster]

from Bouvier's Law Dictionary, Revised 6th Ed (1856)

SCANDALUM MAGNATUM. Great scandal or slander. In England it. is the slander 
of the great men, the nobility of the realm.