Definitions for "Deadlight"
A strong shutter, made to fit open ports and keep out water in a storm.
a strong shutter over a ship's porthole that is closed in stormy weather
steel, hinged cover to protect the portholes glass in heavy weather or to prevent lights inside the ship from showing outside; it can be mechanically secured by screws and nuts
Space immediately above the window architrave and below the ceiling and cornice.