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)
Derived from:
knock
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