lookout

Etymology

From the verb phrase look out.

noun

1. A vantage point with a view of the surrounding area.
2. A session of watching for an approaching enemy, police, etc.
   We kept a lookout all night, but nobody came.
3. A person on watch for approaching enemy, police, danger, etc.
   The raid failed when the lookout noticed the enemy group.
   A lack of lookouts was partially responsible for the deaths of two track workers at Margam East Junction in south Wales on July 3, according to an interim report published by the Rail Accident Investigation Branch on December 5. … "The absence of a lookout with no involvement in the work activity removed a vital safety barrier," says the report. December 18 2019, Andrew Roden, “Absence of lookouts contributed to Margam deaths”, in Rail, page 20
4. A subject for observation; a prospect or view.
5. One's perspective, outlook; hence, one's responsibility. (used with a possessive pronoun or a noun in a possessive form).
   Every person's interest is his own lookout.
6. An observation window.
   Twenty-one of these vehicles were later converted into bogie brake vans for freight service. … The extreme width over the side lookouts is 9 ft. 1941 February, Railway Magazine, page 75, untitled paragraph
7. (construction) A joist that extends in cantilever out from the exterior wall (or wall plate) of a building, supporting the roof sheathing and providing a nailing surface for the fascia boards.