Not truely a real word in the dictionary....yet. More known as being an onomatopoeia. Can be like saying "really" when you disagree with something (think of how you may use "Psh" in common language) and has to be used in the right form or just sounds like you have a water leak. Invented by a blonde chick that loves Scooby-Doo to much and known to not possibly speak english quite swell.
Must use hand in the air type motion, for instance like Hitlers salute except you point at the person with a "really like wtf" face aha!
friend: "Hey did you pass the math test?"
reply: "Pshk, no!"