ăcaustus, a, um, adj., = ἄκαυστος,
incombustible; hence subst. m. (sc. lapis), the carbuncle , since it was regarded as incombustible: acaustoe (i. e. ἄκαυστοι), Plin. 37, 7, 25, § 92; v. Sill. a. h. l.