knock on

7 8.2

The illegal action of hitting the ball forward with the hand or arm while trying to catch it

noun

Jargon

: knock on

Examples

There is a knock on the door.

Fiction book (1992)
Early one morning, there was a knock on the door, and someone left a package.

Fiction book (1993)
There was a knock on the door, and we swiveled our heads to look down the hall.

Fiction book (1999)
She was halfway through the dishes when she heard a knock on her kitchen door.

Fiction book (1999)
There was a knock on the door, followed by a fanfare of trumpets and a peal of silvery bells.

Fiction book (1993)
In rugby, a knock on occurs when a player accidentally knocks the ball forward with their hand.
The referee called a foul after the player made a knock on during the game.
During the match, his knock on led to a scrum for the opposing team.

Surface Forms

knock on singular

knock ons plural

Morphology

knock + on

The verb 'knock' (to hit) gives a clear core idea of striking, so a B1 learner who knows the constituents could guess this is about hitting the ball. However, the specific sense—an illegal forward contact with the hand in rugby—and the role of 'on' are sport-specific and not fully predictable from the parts, so prior exposure is needed to understand the exact rule.

Etymology

Knock on comes from rugby and the simple image of a player accidentally hitting the ball forward with a hand or arm: the player knocks the ball on, pushing it 'forward' instead of catching it. So, a knock on means that illegal action which makes play stop.