Dictionary Definition

observer

1 a person who becomes aware (of things or events) through the senses [syn: perceiver, beholder]

2 an expert who observes and comments on something [syn: commentator]

User Contributed Dictionary

One who watches, monitors or takes notice

Most impartial observers agreed that Sampras had not served well.
One who adheres or follows laws, guidelines, etc.

I shall be an observer of the local customs.
A person sent, as a delegate, to a meeting or other function to monitor but not to participate

The UN sent many observers to the country's first elections.
A crew member on an aircraft who makes observations of enemy positions or aircraft

The only crew-member to survive the crash was the Canadian observer.
A sentry etc manning an observation post

We waited till dusk when the observers vision was poorest.

A person who adheres or follows laws, guidelines, etc.

he who watches, monitors or takes notice

A person sent, as a delegate, to a meeting or other function to monitor but not to participate

A crew member on an aircraft who makes observations of enemy positions or aircraft

A sentry etc manning an observation post

observer

Observer can have the following meanings:

Any person who is observing
A person who is permitted to observe, and report on, the proceedings of an assembly or a meeting but who is not permitted to vote or otherwise participate.
An aircrew member of a (military) aircraft responsible for searching (usually visually) for intelligence, opposing forces, survivors, and other occurrences of interest to the mission
Observer (special relativity), a notion from the special relativity theory
In information theory, any system which receives information from an object.
A state observer in a control application: in most control systems, not all state variables of the plant can be measured; but in an observable plant the state can be estimated with the help of a state observer, the result often being used for full state feedback.
Observer (Software), a PHP/MySQL-based network management system
The Observer, a UK Sunday newspaper
The Texas Observer, an American political magazine
A Sri Lankan Sunday and evening newspaper
A design pattern used in computer programming: see Observer pattern
An airborne reconnaissance robot used by the Protoss in the StarCraft series.
Brain Guy, one of many omnipotent aliens in Mystery Science Theater 3000
"The Observer", a track from the Flaming Lips' 1999 album The Soft Bulletin

TV-viewer, ace, air force, beholder, bird-watcher, bomber pilot, bystander, combat pilot, drugstore cowboy, examinant, examiner, eyewitness, fighter pilot, flyboy, gaper, gazer, gazer-on, girl-watcher, goggler, inspector, investigator, kibitzer, looker, looker-on, military pilot, naval pilot, ogler, onlooker, perceiver, percipient, scrutineer, seer, sidewalk superintendent, spectator, spectatress, spectatrix, suicide pilot, televiewer, television-viewer, tester, video-gazer, viewer, visitator, visitor, watcher, witness