noun (n)

• a piece of armor plate (with eye slits) fixed or hinged to a medieval helmet to protect the face(noun.artifact)

  Synonym:
  vizor
  

  source: wordnet30
• a brim that projects to the front to shade the eyes(noun.artifact)

  Synonym:
  bill, eyeshade, peak, vizor
  

  source: wordnet30
• A part of a helmet, arranged so as to lift or open, and so show the face. The openings for seeing and breathing are generally in it.(noun)

  source: webster1913