Source : Webster's Revised Unabridged Dictionary (1913)

Withstander \With*stand"er\, n.
   One who withstands, or opposes; an opponent; a resisting
   power.

Source : WordNet®

withstander
     n 1: an opponent who resists with force or resolution; "obstinate
          withstanders of innovation"
     2: a fighter who holds out against attack [syn: {defender}]