Definition of pyrophoric in US English:



  • 1Liable to ignite spontaneously on exposure to air.

    • ‘It is pyrophoric, generating intense heat on impact, penetrating a tank because of the heavy weight of its metal.’
    • ‘In addition to the radioactivity, DU is chemically toxic, pyrophoric and usually spreads aerolisized particles over a large area on impact.’
    • ‘We have a lot of pyrophoric substances in an organic chemistry lab - things that burst into flame when they encounter normal air.’
    • ‘It is pyrophoric, burning spontaneously on impact, and extremely dense.’
    1. 1.1 (of an alloy) emitting sparks when scratched or struck.
      • ‘One of the oldest uses for praseodymium is in the manufacture of misch metal, a pyrophoric metal.’
      • ‘The Army and other pyrophoric uranium munitions NRC licensees should admit the quantity of UO3 vapor produced by such weapons.’
      • ‘Aside from being very dense and pyrophoric, depleted uranium shells also have a nasty tendency to vaporise.’


Mid 19th century: from modern Latin pyrophorus, from Greek purophoros ‘fire-bearing’, from pur ‘fire’ + pherein ‘to bear’.