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.

Source: Webster's Revised Unabridged Dictionary (1913)