The definition of brimstone is sulfur, usually referenced when describing hell.
(noun)An example of brimstone is something that burns in the fictional images of hell.
See brimstone in Webster's New World College Dictionary
noun
Origin: ME brimston < OE brynstan: see burn & stone
See brimstone in American Heritage Dictionary 4
noun
Origin:
Origin: Middle English brimston
Origin: , from Old English brynstān; see gwher- in Indo-European roots
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