pyrophoric
Concise Oxford English Dictionary © 2008 Oxford University Press:
pyrophoric /ˌpʌɪrə(ʊ)ˈfɒrɪk/
▶adjective
- 1 liable to ignite spontaneously in air.
- 2 (of an alloy) emitting sparks when scratched or struck.
– origin C19: from mod. L. pyrophorus, from Gk purophoros ‘fire-bearing’.
'pyrophoric' also found in these Oxford entries:

