- A hinged, usually metal fixture on the exterior face of a door, used for striking or knocking.
- noun a borrower of money, debtor, defaulter. The word is used to refer to personal debtors, those reneging on hire purchase agreements or, by prisoners in particular, to those who welch on a bet – a sense in which the word was used in sporting circles before World War II. The origin of this use of knock is not completely clear; it may simply have the sense of to damage (financially), come from an obsolete word meaning to borrow, or may refer to some more specific practice such as rapping on a table to indicate one’s inability to continue in a card game.
- noun a breast. A rarely heard singular form of knockers.