pyrophoric

UK: /ˌpaɪrəʊˈfɒrɪk/ US: (pī′rə fôr′ik, -for′-)

WordReference Random House Unabridged Dictionary of American English © 2025

py•ro•phor•ic  (pī′rə fôr′ik, -for′-), adj. [Chem.]

1. Chemistry capable of igniting spontaneously in air.

• Greek pyrophór(os) fire-bearing (see pyro-, -phorous) + -ic
• 1830–40

Collins Concise English Dictionary © HarperCollins Publishers::

pyrophoric / ˌpaɪrəʊˈfɒrɪk/, pyrophorous / paɪˈrɒfərəs/ adjective

1. (of a chemical) igniting spontaneously on contact with air
2. (of an alloy) producing sparks when struck or scraped: lighter flints are made of pyrophoric alloy

Etymology: 19th Century: from New Latin pyrophorus, from Greek purophoros fire-bearing, from pur fire + pherein to bear