Motormouth (noun)

1. A person who talks excessively, quickly and continuously.
2. A person who talks a lot, especially without thinking before speaking.

Origin:

A motormouth is someone who talks excessively, quickly and continuously. this term is derived from the word "motor" which means machine that converts fuel energy into mechanical motion, and "mouth" which means the organs of speech, the term was first used in the 1920s.

Examples:

1. She was a real motormouth and never seemed to stop talking.
2. He was a motormouth, and no one wanted to talk to him.
3. He was a classic motormouth, always talking, always interrupting.
4. She was a motormouth, but that's just the way she is.
5. He's such a motormouth, I can hardly get a word in edgewise.