Noun > Knock

Noun – Knock

1 a (count) : a hard, sharp hit

He gave him a knock on the head.

1 b (count) : the sound made by a hard, sharp hit

There was a loud knock at the door.

2 (count) informal : an experience that makes you less confident or successful for a period of time : a difficult or painful experience

She took some knocks early in her career.

Most performers have their share of knocks (=setbacks) on their way to stardom.

3 (count) informal : a critical or negative comment

He likes praise but can’t stand the knocks.

4 : a loud noise produced by an engine when it is not working properly

(count)

We heard a knock in the engine.

(noncount)

a type of fuel that reduces engine knock