incombustible /ˌɪŋkəmˈbʌstɪbəl/adjective 1noun 1forms 3 adjective1 •Not capable of catching fire and burning; not flammable.The ash represents the more incombustible mineral matter, usually of the nature of clay or slate. — 1921 noun1 •An incombustible substance. formsincombustibles · more incombustible · most incombustible
