DEADLIGHT

deadlight

(noun) a strong shutter over a ship’s porthole that is closed in stormy weather

Source: WordNet® 3.1

Etymology

Noun

deadlight (plural deadlights)

(nautical) 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.

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

(figurative) An eyelid.

Source: Wiktionary

Dead"light`, n. (Naut.)

Definition: A strong shutter, made to fit open ports and keep out water in a storm.

Source: Webster’s Unabridged Dictionary 1913 Edition