Lewis & Short

succēdānĕus or succīdāneus (on the latter very ancient orthog. cf. Gell. 4, 6, 4 sq.), a, um, adj. [succedo], that follows after or succeeds to something, that supplies the place of something, substituted, succedaneous: hostia, quae ad aras adducta est immolanda, si casu effugeret, effugia vocari veteri more solet: in cujus locum quae supposita fuerat, succidanea, Serv. Verg. A. 2, 140; cf. Gell. l. l.; and Fest. p. 302 Müll.: si quid succidaneis opus esset, robus succederet, S. C. ap. Gell. 4, 6, 2: asinus pro homine succidaneus, App. M. 8, p. 213, 29: ut meum tergum stultitiae tuae subdas succidaneum? Plaut. Ep. 1, 2, 37: subrogare aliquem succedaneum, Cod. Just. 11, 65, 3: avum suum Pharnacem succedaneum regi Pergameno Eumeni datum, Just. 38, 6, 2.
Subst.: succēdānĕus, i, m., a substitute, representative; with gen., Dig. 17, 8, 4: functionis, Cod. Just. 10, 31, 27: alieni periculi, Dig. 26, 7, 3 fin.