n. A watching for the appearance or occurrence of anything, especially from without; vigilant observation or scrutiny; watch: as, to keep a good lookout at sea; to be on the lookout for an opportunity.n. A place where a watch is kept; a post of external observation: as, the lookout on a ship's mast.n. A person or party engaged in keeping watch, especially for things outside.n. The subject of observation or vigilance; something to be watched for or guarded against: as, every man's interest is his own lookout.n. A prospect or view; an outlook.n. In car-building, a glazed clearstory on the roof of a caboose, designed to enable the train-hands to obtain a clear view over the tops of the cars in a train.