pyrophoric
\ pahy-ruh-FAWR-ik, -FOR- \, adjective;
1.Chemistry . capable of igniting spontaneously in air.
Quotes:
Plutonium is highly reactive and pyrophoric . The ceramic crucibles are also inert and nonreactive.
-- Tom Clancy, "The Sum of All Fears," 1991
And since " pyrophoric " just means "inflames on contact with air" it is highly misleading to tell librarians that it isn't pyrophoric in a vacuum.
-- Nicholson Baker, "Double Fold," 2001
Origin:
Pyrophoric entered English in the late 1700s from the Greek root pyrophóros meaning "fire-bearing."
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