butt sick adj.:
1. A general feeling of frustration and/or anger.
2. Diarrhea
"This project is making me butt sick."
"That chilli made me butt sick."
A bad case of diarrhea. Often used when it is not certain which end you are going to be sick from.
Man, Willy got so sick from that hot sauce.
Butt Sick or Mouth Sick?
Butt Sick