lookout — Cape, a sandy reef in the Outer Banks, off E North Carolina, SW of Cape Hatteras: lighthouse.
guard — to keep safe from harm or danger; protect; watch over: to guard the ruler.
keeper — a person who guards or watches, as at a prison or gate.
sentinel — a person or thing that watches or stands as if watching.
sentry — a soldier stationed at a place to stand guard and prevent the passage of unauthorized persons, watch for fires, etc., especially a sentinel stationed at a pass, gate, opening in a defense work, or the like.
watchman — a person who keeps guard over a building at night, to protect it from fire, vandals, or thieves.
security guard — a uniformed guard employed by a bank, airport, office building, etc., to maintain security.
