knocks

Knocks is a term with several related meanings tied to the act of striking or the sound produced by striking. As a noun, a knock is the act of striking something to create a noise, or the noise itself, such as a knock on the door or a dull thump from a table being struck.

As a verb, to knock means to strike something with a quick blow, or to cause something to collide. It can describe a door being rapped to announce a visitor, or objects being bumped and moved. Metaphorically, knock can mean to criticize or undermine, as in knocking a plan or a performance.

In sports and entertainment, a knock may refer to a decisive strike or a blow that leads to a knockdown or knockout, particularly in boxing or mixed martial arts. The term knockout (KO) denotes a fighter being unable to continue.

In engineering and mechanics, engine knock, or detonation, is an undesirable premature combustion of the fuel-air mixture in an internal combustion engine. A knock sensor detects such conditions to adjust timing and prevent damage.

Culturally, knock-knock jokes are a well-known format built on a call-and-response sequence that begins with "Knock knock."

Etymology traces the word to the onomatopoeic imitation of the sound produced by striking, with cognates in many languages. See also knock on wood, knockout, and knock-knock joke.