Dictionary.net

Lat In Roman law. Certain classes of things which could not be aliened or transferred except by means of a certain formal ceremony of conveyance called "maneipatio," (q. v.) These included laud, houses, slaves, horses, and cattle. All other things were called "res nee mancipi." The distinction was abolished by Justinian. The distinction corresponded as nearly as may be to the early distinction of English law into real and personal property; res mancipi being objects of a military or agricultural character, and res nec mancipi being all other subjects of property. Like personal estate, res nec mancipi were not originally either valuable in se or valued. Brown.