自し然ぜん発はっ火か

noun

spontaneous combustion

Technical term for a fire that starts without an external ignition source, often due to chemical or biological heat buildup.

• 油あぶらのついた布ぬのが自し然ぜん発はっ火かする危き険けんがある。

  There is a risk of spontaneous combustion from oily rags.