Stands for judgment fox. When you disapprove of someone or something and feel like you wish to judge them, you make a fox with your hand and point it at them. Best when accompanied by a Judge Judy-like stare of pure unadulturated judgment.
Person 1: "Gurrl, I just went and got my stomach pumped at the hospital so I chug some more booze. ROFL!"
Person 2: *J-foxes*