Chamfron

n. armor to protect the head of a horse

Barding (also spelled bard or barb) is armour for horses. During the late Middle Ages as armour protection for knights became more effective, their mounts became targets. This tactic was effective for the English at the Battle of Crécy in the fourteenth century where archers shot horses and heavy infantry killed the French knights after they dismounted. Barding developed as a response to such events.
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Noun
1. medieval plate armor to protect a horse's head
(synonym) chanfron, testiere, frontstall, front-stall
(hypernym) armor plate, armour plate, armor plating, plate armor, plate armour

(n.)
The frontlet, or head armor, of a horse.
  

The plate defense guarding the horse's face. 14th century examples seem to be very rare, with little refinement, using globular pierced defenses for the eyes. The chamfron became well developed in the 15th century, when the horse was more fully armoured in plate. The Crinet , another portion of horse barding , defended the horse's neck.