Using Foursquare to see who has checked into the venue you are at, and then looking around to try and find them.
Square Stalker: *shows friend picture from Foursquare profile on phone*
Normal Friend: What?
Square Stalker: This person is here. Do you see them anywhere?
Normal Friend: Dude stop square stalking, weirdo.
by AtlasRider September 9, 2011
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