noun
flint fire; flash
Literally the spark from striking flint; often used metaphorically for something extremely brief or instantaneous. Common in the idiom 石火の光 (a flash of light) or in expressions like 石火の如く (like a flash).
石火の光のような一瞬の出来事だった。
It was a momentary event, like a flash of light from flint.
彼の動きは石火の如く素早かった。
His movement was as quick as a flash.