deadlight

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.

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

An eye.

Here you comes and tells me of it plain; and here I let him give us all the slip before my blessed deadlights!

An eyelid.

He had one hand on the bounce bottle—and he'd never let go of that since he got back to the table—but he had a handkerchief in the other and was swabbing his deadlights with it.