The Collaborative International Dictionary of English v.0.48:

Varec \Var"ec\, n. [F. varech; of Teutonic origin. See Wrack
   seaweed, wreck.]
   The calcined ashes of any coarse seaweed used for the
   manufacture of soda and iodine; also, the seaweed itself;
   fucus; wrack.
   [1913 Webster]