noun (n)

• a window above a door that is usually hinged to a horizontal crosspiece over the door(noun.artifact)

  Synonym:
  fanlight, transom window
  

  source: wordnet30
• a horizontal crosspiece across a window or separating a door from a window over it(noun.artifact)

  Synonym:
  traverse
  

  source: wordnet30
• A horizontal crossbar in a window, over a door, or between a door and a window above it. Transom is the horizontal, as mullion is the vertical, bar across an opening. See Illust. of Mullion.(noun)

  source: webster1913