Source : Webster's Revised Unabridged Dictionary (1913)

Brimstone \Brim"stone\, n. [OE. brimston, bremston, bernston,
   brenston; cf. Icel. brennistein. See {Burn}, v. t., and
   {Stone}.]
   Sulphur; See {Sulphur}.

Brimstone \Brim"stone\, a.
   Made of, or pertaining to, brimstone; as, brimstone matches.

         From his brimstone bed at break of day A-walking the
         devil has gone.                          --Coleridge.

Source : WordNet®

brimstone
     n : an old name for sulfur [syn: {native sulfur}, {native
         sulphur}]