deadlight

/D EH1 D L AY0 T/
noun
  1. 1

    A strong (often wooden) shutter fitted over a porthole, that can be closed in bad weather to keep water out and discourage the glass windows from breaking.

  2. 2

    A deck prism, a device to allow light into the cabin of boat through the deck.

  3. 3

    An eyelid.

Source: https://en.wiktionary.org/wiki/deadlight