A lookout (vantage point with a view of the surrounding area)
A place where stars, planets and other celestial bodies are observed, usually through a telescope; also place for observing meteorological or other natural phenomena.
Someone who keeps vigil.
A guard.
A kind of angel appointed to watch over the human realm, in particular one of those who became fallen angels and begot the Nephilim.
Someone who observes something closely for professional reasons, such as an analyst or pundit.
A political representative aligned with a candidate sent to observe elections to report on irregularities. A scrutineer.