Uttered hastily when you did something you:
A) Realize you should not have done and will never consciously do again, or
B) Acknowledge doing, but got too wasted to clearly remember.
Sidenote: Is commonly used just before Not so much.
A)"I can't believe you wore such excessive amounts of spandex back in high school."
"Yeah... yeahbutno. Not so much."
B)"Dude, you were wasted, you totally got with her. Don't you remember?"
"Yeah... Yeahbutno. Not so much."
Used in the teenager sketch in little britain.
Teacher: Why havnt you done your homework
Girl: I have
T: No you havnt
G:what it is right is *speaks really fast*
Synonymous with nobutyeah.
So... ummmm.... yeahbutno