Mancipatio. Every father, in the Roman law, had such an authority over his son, that before the son could be released from his subjection and made free he must be twice sold and bought, his natural father being in the first instance the vendor. The vendee was called pater fiduciarius. After this fictitious bargain, the pater fiduciarius sold him again to his natural father, who could then, but not till then, manumit or make him free. The imaginary sale was called mancipatio; and the act of giving him liberty, or setting him free, was called emancipatio.
Also selling or alienating of certain lands by the balance or money paid by weight, and in the presence of five witnesses. This mode of alienation took place only among Roman citizens, and that only in respect to certain estates situated in Italy, which were called mancipia, Encyc. Londin. Abolished by Justinian, when he obliterated the distinction between things mancipi and things nec mancipi. See Sand. Just.; Maine's Ancient Law.