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Someone who is doing something wrong and is being obvious or looking guilty.
Somone is dealing crack in front of a cop. "look at that sketch monster!"
by carla and tracy October 26, 2007
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some one who does or says sketchy things. overly sketchy, suspicious.
ruby: OMG guess what matt told me last night?
catherine: what?
ruby: he said we should go to the woods at night
catherine: what a sketch monster!
by candycanelegs September 03, 2012
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One who is sketchy in monstrous proportions.

One who is very, very suspicious or acts in suspicious ways.
(Random guy hides behind a wall.)
Person 1: Dude, look at that sketchmonster behind that wall.
Person 2: Yeah, seriously. Look at him. Standing behind that wall.
by Pdoany. February 25, 2009
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