machine gun mouth
A machine gun mouth is someone who talks so much and so fast it feels like you're being hit with words from every direction.
My dad talked about his job for 2 hours straight. I wanted to scream and hide under my bed.
My friend talked about his pet turtle for 15 minutes. I was ready to die.
My teacher started explaining the moon phases like it was a mystery novel. I wanted to throw my pencil at her.