This is something you say to someone when they do or say something extremely stupid. If someone does or says something stupid you say "thats a chop" and karate chop the back of their neck. The strength of the chop depends on how stupid the words or actions of the person was.
Nick: "Totally did not do my homework last night. Yolo!"
Jon: "Thats a chop"
by Dr.Chopper December 2, 2012
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