The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Pyrophorus
    n 1: tropical click beetles [syn: Pyrophorus, genus
         Pyrophorus]