Stands for "Trippin Nuts", slang for being high or drunk at a large degree. Usually pronounced as (tee-end) in a sentence. It's also an abbreviation for the state Tennessee, various schools, and businesses. It is currently not a popular slang but is mostly used in "stoner" communities. This saying's possible origin could be central Iowa or Colorado.
-correct me if I'm wrong.
1. Bob - "Hey Rick how ya doin?"
Rick - "I'm f**kin' TN'd man!"
2. Bob - "Hey Rick where ya from?"
Rick - "Parkview, TN (tennessee) and you?"
3. Bob - "I'm from Narnia man"
Rick - "Yeeahh! Bob is soo TN'd guys!"