knocker
knocker , noun
1.
One who, or that which, knocks; specifically, an instrument, or kind of hammer, fastened to a door, to be used in seeking for admittance.
Shut, shut the door, good John! fatigued, I said;
Tie up the knocker; say I'm sick, I'm dead.
2.
A person strikingly handsome, beautiful, or fine; one who wins admiration; a “stunner.” [Slang.]
3.
A species of large cockroach, especially Blabera gigantea, of semitropical America, which is able to produce a loud knocking sound.
4.
a woman's breast. [usually used in pl.; vulgar]