knocking

knocking — verb

1. to hit a door, window, or other surface with your hand, a tool, or a hard object

1.verbintransitiveB1
Definition

to hit a door, window, or other surface with your hand, a tool, or a hard object, usually to get someone's attention or to show that you are there.

Example

Gabriel knocked on the classroom door before entering.

knock + on + door + before entering

The postman knocked three times, then left a parcel on the step.

knock + number of times for attention

Common collocations
  • knock on
  • knock at
  • knock loudly
  • knock gently
  • knock three times
Synonyms
  • tap

    lighter, quieter; often with fingertips

  • rap

    sharper, quicker; often with knuckles

  • bang

    louder and more forceful

Grammar Patterns

knock + on/at + noun

Usage Note

The surface being hit is introduced by 'on' (most common in British English) or 'at' (more common in American English). This sense does not take a direct object — you knock on a door, not knock a door.

Common Mistakes

I knocked the door but no one came.
I knocked on the door but no one came.
When you hit a surface to get attention, you need 'on' or 'at'.

2. to hit someone or something with enough force that they fall to the ground, move

2.verbtransitiveB1
Definition

to hit someone or something with enough force that they fall to the ground, move aside, or are sent in a particular direction.

Example

Darius accidentally knocked over a glass of water while reaching for his keys.

knock + over + glass — accidental

The strong wind knocked the garden chairs onto the grass.

wind + knocked + chairs — inanimate subject

Common collocations
  • knock over
  • knock down
  • knock off
  • knock aside
  • knock someone to the ground
Synonyms
  • tip over

    slower, more gradual falling

  • push over

    emphasises the pushing motion, less forceful

  • bowl over

    specifically of a person being knocked to the ground

Antonyms
  • right

    to set something upright again

  • steady

    to prevent something from falling

Grammar Patterns

knock + object + over/off/down

Usage Note

Nearly always used with a particle (over, off, down, aside) that tells you the result of the impact. Without the particle, the meaning changes to sense 1 (HIT SURFACE). The object must be stated — you knock something over, not just knock over.

Common Mistakes

❌ 'I knocked the glass over when I bumped the table.' (correct as is) — This is the correct structure. The mistake is often dropping the particle: ❌ 'I knocked the glass.' (sounds like sense 1 — hitting it, not causing it to fall).

3. to say critical or disapproving things about someone or something, often in a wa

3.verbtransitiveB2
Definition

to say critical or disapproving things about someone or something, often in a way that seems unfair or unnecessarily negative.

Example

Paloma criticised the plan, but her boss told her to stop knocking it.

stop + knocking — informal pattern for 'stop criticising unfairly'

The newspaper keeps knocking the government's education policies.

keeps + knocking — repeated criticism, informal

Common collocations
  • stop knocking
  • always knocking
  • keep knocking
  • knocking [someone/something]
Synonyms
  • criticise

    more neutral and formal; does not imply unfairness

  • put down

    similar register; emphasises making someone feel small

  • disparage

    formal; implies speaking of something as low or unworthy

Antonyms
  • praise

    to express approval or admiration

  • compliment

    to say something positive about someone

Grammar Patterns

knock + noun phrase (person/thing/idea)

Usage Note

Informal register. Stronger and more dismissive than 'criticise'. Often implies the criticism is habitual, petty, or undeserved. Common in phrases like 'stop knocking [sb/sth]' and 'always knocking [sb/sth]'. Less common in formal writing.

Common Mistakes

The report knocks the company's financial decisions.' (if the report is formal/professional)
The report criticises the company's financial decisions.
In formal contexts, use 'criticise' instead of 'knock'.

4. to remove a wall or partition that separates two rooms, joining them together to

4.verbtransitiveB2
Definition

to remove a wall or partition that separates two rooms, joining them together to create a single larger living space.

Example

The couple decided to knock through the wall between the kitchen and the dining room.

knock + through + wall — phrasal verb pattern

Harper knocked the two small bedrooms into one to make a larger space.

knock + [room] + into + [room] — combining rooms

Common collocations
  • knock through
  • knock into
  • knock a wall through
  • knock two rooms together
Synonyms
  • remove

    more formal; used in professional construction contexts

  • take down

    more general; can refer to any structure, not just walls

Antonyms
  • put up

    to build a wall where there was none

  • erect

    formal; to build or construct

Grammar Patterns

knock + through + wall

knock + room + into + room

Usage Note

Chiefly British English. Very common in home renovation contexts. The wall must be checked by a professional because some walls are 'load-bearing' — knocking them out without support can cause the building to collapse. Usually used with 'through' or the pattern 'knock X into Y'.

Common Mistakes

We knocked the wall to make the room bigger.
We knocked through the wall to make the room bigger.
The phrasal verb 'knock through' is the correct form; 'knock the wall' alone sounds like sense 1 (hitting it).

5. (of a car or other vehicle engine) to make a sharp repeating sound when the fuel

5.verbintransitiveB2
Definition

(of a car or other vehicle engine) to make a sharp repeating sound when the fuel-air mixture burns unevenly or when a mechanical part works loose, signalling a fault that needs repair.

Example

The car engine started knocking, so Vinícius drove it straight to the garage.

engine + started knocking → needs repair

Using low-quality fuel can cause an older engine to knock badly.

fuel quality + cause + engine to knock

Common collocations
  • engine knocks
  • knocking sound
  • start knocking
  • stop knocking
Synonyms
  • ping

    a lighter, higher-pitched engine sound, similar to knock but less severe

  • rattle

    a loose, shaking sound from a different type of mechanical problem

Grammar Patterns

engine + is knocking

start + knocking

Usage Note

Used in automotive contexts. The verb is most common in continuous tenses ('the engine is knocking'). Engine knock is also called 'pinking' or 'detonation'. This is distinct from the normal sound of a running engine.

Common Mistakes

The engine is knocking, so I need more oil.
The engine is knocking, so I need to get it checked by a mechanic.
Knocking is not fixed by adding oil; it usually requires professional diagnosis.

6. (of a household pipe, radiator, or boiler) to make a regular banging or tapping

6.verbintransitiveB2
Definition

(of a household pipe, radiator, or boiler) to make a regular banging or tapping sound as water or steam flows through it, often caused by trapped air, loose fittings, or changes in temperature.

Example

The radiator knocks every time the central heating comes on.

radiator + knocks + when heating starts

Élise called the plumber because the pipe in the bathroom was knocking all night.

pipe + was knocking + calls plumber — repair needed

Common collocations
  • pipe knocks
  • radiator knocks
  • knocking noise
  • stop knocking
Synonyms
  • bang

    a louder, more explosive sound from pipes

  • rattle

    a continuous shaking noise from loose pipe fittings

Grammar Patterns

pipe + is knocking

knocking + in + pipe/radiator

Usage Note

Common in British English for describing plumbing issues. The knocking is often called 'water hammer' in technical terms. Differs from sense 5 (ENGINE NOISE) in that the source is household plumbing, not a vehicle engine.

Common Mistakes

The pipe is knocking, so the engine needs fixing.
The pipe is knocking, so I need to call a plumber.
Pipes are plumbing concerns, not engine concerns.

Word family

  • knock
    verbB1
  • knock
    nounB1
  • knocker
    nounB2
  • knock-on
    adjectiveC1
  • knockout
    nounB2
  • knockdown
    adjectiveC1

Synonym discussion

Sense: verb/1

All four words describe hitting a surface, but they differ in force, sound, and purpose. 'Knock' (B1) is the general word for hitting a door or window to get attention — it's the most neutral and widely used. 'Tap' (B2) is lighter and quieter, often done with the fingertips or a soft object; you might tap someone on the shoulder or tap a screen to open an app. 'Rap' (B2) is sharper and more urgent, typically with knuckles against a hard surface — a teacher might rap on a desk to quiet a noisy class. 'Bang' (B1) is much louder and more forceful, often suggesting impatience or anger — for example, someone who is angry might bang on the door with a fist. In everyday situations, 'knock' is the safest and most natural choice for polite attention-seeking, while the others carry stronger implications about the manner or mood of the person doing the hitting.

knock ↗tap ↗rap ↗bang ↗

Common collocations

Nouns

Adverbs

Phrases

  • knock on the door
  • knock at the window
  • knock someone over
  • knock through a wall

Prepositions

Etymology

Proto-GermanicOld EnglishMiddle EnglishEnglish

The word 'knock' comes from Old English 'cnocian' (to strike, beat, or pound), which is likely related to the Proto-Germanic root *knuk- — an onomatopoeic verb that imitates the sound of a sharp blow. Similar words exist in other Germanic languages, such as Old Norse 'knoka' (to beat) and Middle Dutch 'knoken'. The informal sense 'to criticise' first appeared in late 19th-century American English, and the automotive sense (engine knocking) dates from the early 20th century as cars became widespread.