/nok"euhr/ , n.
1. a person or thing that knocks.
2. a hinged knob, bar, etc., on a door, for use in knocking.
3. Informal. a persistent and carping critic; faultfinder.
4. Slang ( vulgar ). a female breast.
5. on the knocker , Brit. Slang. canvassing or selling door-to-door.
[ 1350-1400; ME; see KNOCK, -ER 1 ]