i don't give a brass razoo
A very loud and angry way of saying you don’t care, and you’re going to make sure everyone knows it.
You said I’m fat. I don’t give a brass razoo, I’m gonna eat your lunch and laugh at you.
Your dog chased me. I don’t give a brass razoo, I’m gonna throw your dog in the lake.
Your grades are bad. I don’t give a brass razoo, I’m gonna draw a mustache on your teacher’s face.