‖ adpromissorRom. Law.|ˌædprəʊˈmɪsə(r), -ɔː(r)| [a. L. adprōmissōr one who is security, f.ad- in addition + promitt-ĕre to promise.] One who gives bail or security. 1875Poste Gaius iii. 402 The adpromissor at different epochs of the law appears as sponsor, fidepromissor, fidejussor.