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.