What does knock mean?
Knock is a common English word with several related uses. As a verb, it most often describes striking a door, wall, or other surface with a sharp blow, as in “knock on the door,” and it can also mean making a sound to attract someone's attention. Figuratively, it means to criticize something forcefully, as in “knock the plan,” or to leave someone exhausted, as in “be completely knocked out.” As a noun, a knock is the blow or sound produced by striking, and it can also mean a criticism or disadvantage. The expression “knock, knock” is a familiar spoken interjection used at a door. Although its literal meaning is simple, the word is highly flexible: “knock” can describe a physical action, a sound, an objection, an adverse effect, or a state of fatigue. Its many figurative uses reflect the idea of a knock as a sudden or forceful impact.
To strike a surface with a sharp blow, often making a repeated sound, or to signal one's presence in this way.
"He knocked twice on the office door."
The verb is commonly used with “on,” as in “knock on the door,” although “knock the door” is also standard.
To criticize or question something forcefully, or to cause someone to feel exhausted or weakened.
"Opposition members continued to knock the new policy."
These figurative uses are common in formal debate and informal criticism; “knock” can be somewhat dismissive.
A sharp blow, the sound made by striking a surface, or a criticism or adverse condition.
"There was a knock at the door, followed by silence."
In British English, “a knock-on effect” means an indirect consequence, while “a knock” can refer to a disadvantage such as a financial setback.
A spoken expression used to announce one's presence at a door, usually repeated: “knock, knock.”
"Knock, knock! Is anybody there?"
This is informal and conversational, and is often playful rather than literal.
The plural is used for individual blows or sounds and for figurative disadvantages or criticisms.
"The engine made several knocks before it started."
From a polite request at the door to a forceful objection in debate, knock moves easily from physical blows to figurative impacts.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does knock come from?
The word comes from Old English cnocian, meaning to strike or beat, and probably imitates the sound of knocking. It developed through Middle English into modern English in the form knock. Related words appear in other Germanic languages, including Dutch kloppen and German klopfen. The noun meaning a blow or knocking sound was established alongside the verb, while figurative senses developed later from the ideas of striking, criticizing, and affecting something.
Related word forms
How knock is actually used
The verb is neutral in register when describing a literal blow or a knock at a door, but “knock” can sound informal or dismissive when used figuratively to criticize something. In British English, “knock” is especially common in the expression “knock-on effect,” meaning a consequence or indirect effect. The interjection “knock, knock” is generally playful or conversational.
Easily confused with knock
Knock refers to striking a surface or the sound produced by such a strike, while knock is also a noun for the blow, sound, criticism, or adverse condition.