(noun) - a tower built on the coast that has a bright light in the top of it so ships can see it from a long way away. The light helps sailors know not to go too close to a rocky shore, so they didn't crash. Lighthouses were also used to mark the entrance to a harbor so ships could find where they were going at night.
Bodie Island and Cape Hatteras Lighthouse, North Carolina. Image courtesy of the National Park Service.