In old European law. An assembly of the people; so called from being anciently held in the open air, in some plain capable of containing a large number of persons. In feudal and old English law. A field, or plain. The field, ground, or lists marked out for the combatants in the dueUum, or trial by battle. . Campus Mail. The fieH of May. An anniversary assembly of the Saxons, held on May day, when they confederated for the defense of the kingdom against all its enemies. Campus Martii. The field of March. See Champ dk Mabs.