(1) A person designated to detect and report fires from a ventage point (2) A location from which fires can be detected and reported (3) A fire crew member assigned to observe the fire and warn the crew when there is danger of becoming trapped
A lookout is someone who is watching for danger in order to warn other people about it
If someone keeps a lookout, especially on a boat, they look around all the time in order to make sure there is no danger. He denied that he'd failed to keep a proper lookout that night