Screen looker is someone who spies on their opponents in a split screen multiplayer match. It is used to determine their location, amount of health, and carried weapons. It was an integral part of Goldeneye and Perfect Dark gameplay.

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A screenlooker is anyone who on a multiplayer shooter looks at another player's screen to identify their location and frag them as many times as possible. An example game is Halo 2.

a person who is playing a video game with you and is constantly looking at your screen to see your position

Somebody who attempts to gain an unfair advantage while playing a split-screen video game by looking at their opponents' screen sectors.

A person when Playing Halo uses an enemy players screen to his advantage.

A person who tends to look at other peoples screens in hopes of beating them at any or all first person shooters. He uses the justification that one only plays games to win -- and to achieve this goal it's fine to screen look. A.K.A Brad Baum