The Collaborative International Dictionary of English v.0.48:

Court-martial \Court`-mar"tial\ (k?rt`m?r"shal), n.; pl.
   Courts-martial (k?rts`-).
   A court consisting of military or naval officers, for the
   trial of one belonging to the army or navy, or of offenses
   against military or naval law.
   [1913 Webster]