A small thick disk of glass inserted in a deck, roof, floor, ship's side, etc., to let in light.
A lantern, with a thick glass lens on one side for concentrating the light on any object; also, the lens itself.
A thick knob or protuberance left on glass by the end of the pipe through which it was blown.
A small and thick old-fashioned watch.
A convex lens used to concentrate (refract) light.