knocker

noun

1. (Yiddish) a big shot who knows it and acts that way; a boastful immoderate person
2. a person who knocks (as seeking to gain admittance)"open the door and see who the knocker is"
3. one who disparages or belittles the worth of something
4. either of two soft fleshy milk-secreting glandular organs on the chest of a woman
5. a device (usually metal and ornamental) attached by a hinge to a door