/ ˈnɒkə(r); NAmE ˈnɑːk-/ noun
1.
(also ˈdoor knocker ) [ C ] a metal object attached to the outside of the door of a house, etc. which you hit against the door to attract attention
2.
[ C ] ( informal ) a person who is always criticizing sb/sth
3.
knockers [ pl. ] ( taboo , slang ) an offensive word for a woman's breasts