Incombustible \In`com*bus"ti*ble\, a. [Pref. in- not + combustible: cf. F. incombustible.] Not combustible; not capable of being burned, decomposed, or consumed by fire; uninflammable; as, asbestus is an incombustible substance; carbon dioxide is an incombustible gas. {Incombustible cloth}, a tissue of amianthus or asbestus; also, a fabric imbued with an incombustible substance. -- {In`com*bus"ti*ble*ness}, n. -- {In`com*bus"ti*bly}, adv.