Tungsten : A hard brittle metallic element (W) which in finely divided form is highly flammable and may ignite spontaneously; it is used in the filaments of incandescent lightbulbs. See: Wolfram
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}