Source : Webster's Revised Unabridged Dictionary (1913)

Crossbar \Cross"bar`\ (-b[aum]r`), n.
   A transverse bar or piece, as a bar across a door, or as the
   iron bar or stock which passes through the shank of an anchor
   to insure its turning fluke down. --Russell.

   {Crossbar shot}, a projectile which folds into a sphere for
      loading, but on leaving the gun expands to a cross with a
      quarter ball at the end of each arm; -- used in naval
      actions for cutting the enemy's rigging.