knocker

noun

1. 1

   a device (usually metal and ornamental) attached by a hinge to a door

2. 2

   either of two soft fleshy milk-secreting glandular organs on the chest of a woman

3. 3

   one who disparages or belittles the worth of something

4. 4

   a person who knocks (as seeking to gain admittance)

   open the door and see who the knocker is

5. 5

   (Yiddish) a big shot who knows it and acts that way; a boastful immoderate person