Pyrophorus \Py*roph"o*rus\, n. [NL. See Pyrophorous.]

(Old Chem.) Any one of several substances or mixtures which phosphoresce or ignite spontaneously on exposure to air, as a heated mixture of alum, potash, and charcoal, or a mixture of charcoal and finely divided lead.

Source: Webster's Revised Unabridged Dictionary (1913)