A manifestation of your own mind
Your brain is a loudmouth who won’t shut up during your quiet time
You told your teacher you had a brain like a loudmouth. She said, 'That’s why you’re late to every class.'
You said your dog had a brain like a loudmouth. Your dog howled at you.
You told your friend you looked like a loudmouth. They said, 'Thanks, I look like a loudmouth who just got a ticket.'