Source : Webster's Revised Unabridged Dictionary (1913)

Foulder \Foul"der\, v. i. [OE. fouldre lightning, fr. F. foudre,
   OF. also fouldre, fr. L. fulgur. See {Fulgor}.]
   To flash, as lightning; to lighten; to gleam; to thunder.
   [Obs.] ``Flames of fouldering heat.'' --Spenser.