An airlock door on USS Blueback with a small deadlight in the center.

Definition

Noun

  1. A window in a door, deck, etc., to allow light to enter a space.
  2. A wooden or metal cover for a portlight or pothole to protect it from storm or battle damage, and to “darken ship.”

Origin

(first definition) Probably earlier than the 18th century. Another meaning of the word dead is for something inactive or immobile. (second definition) 19th century.

Comments

Deadlights are essentially small windows. Also known as a bullseye. As for the covers over the portlights or portholes, they’re also called storm ports or battle ports.

References

Rogers, J.G. (1985). Origins of Sea Terms. Mystic Seaport.