machine gun mouth
A machine gun mouth is a person who talks so much and so fast it's like they're trying to turn your brain into a blender.
My uncle told me the same story about his dog 5 times in one day. I wanted to throw a pillow at him.
My friend talked about his pizza for 20 minutes. I had to bite my tongue to stay sane.
My teacher explained the meaning of life like it was a math test. I was ready to cry.