Turnt is a variation of "turned" used only to describe when someone is excessively excited or prepared for the current event. In it's entirety, it can commonly be seen used as "turnt up," as in "turned up."
A real Debbie Downer, party pooper, or lame-o, would be someone who is turnt down. They simply are neutral in their stature, and unfit for the current event. Alcohol and or/ drugs would be suitable aid to turning them up.
"David just downed 7 Jager bombs and is fucking that girl from downstairs while wearing your rollerblades, dude! He got so turnt!"
Not to be used in such a manner as this:
"Captain! I have turnt the wheel right of the indigenous islands. These are not the lands you're looking for."