MSU means Making Shit Up.
"Did you hear John Howard* on the telly tonight?"
"MSU?"
"Apparently, if we trust him, everything will stay just fine."
"MSU."
*if you find that you cannot connect with the concept of john howard lying to drive home the usability of this term (you're either one of those lucky foreigners or just plain ignorant) please feel free to add a political liar of your own choice.
