deadlight

(dedlīt′)

noun

  1. a round metal cover placed over a ship's porthole in stormy weather
  2. a window of heavy glass set in the deck or side of a ship
  3. a skylight made so as not to be opened

See deadlight in American Heritage Dictionary 4

noun
  1. Nautical
    a. A strong shutter or plate fastened over a ship's porthole or cabin window in stormy weather.
    b. A thick window set in a ship's side or deck.
  2. A skylight constructed so that it cannot be opened.
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