magmentārĭus, a, um, adj. [magmentum], of or belonging to an addition made to a sacrifice (ante-class.): magmentum a magis, quod ad religionem magis pertinet; itaque propter hoc magmentaria fana instituta locis certis, quo id imponeretur, Varr. L. L. 5, § 112 Müll.
Hence, subst.: magmentārĭum, i, n. (sc. sacellum), a sanctuary for additional sacrifices: putant enim ad me non nulli pertinere magmentarium Telluris aperire, Cic. Har. Resp. 14, 31: magmentarium ἐφ’ οὗ τὰ σπλάγχνα ἀνατιθέμενα τοῖς βωμοῖς προσφέρονται, Gloss. Philox.