1
knocking at/on [something]
常与 at/on 搭配，指明被敲击的对象；此义侧重敲击的动作或声音。
There was a soft knocking on the window.
窗子上有轻轻的敲击声。
敲击；敲门声
knockings — plural of knocking
先理解核心含义，再看它在真实句子里的用法。
敲击；敲门声
An act or sound of knocking on something
There was a soft knocking on the window.
窗子上有轻轻的敲击声。
敲击的动作,或由此产生的声音。
An act in which something is knocked on, or the sound thus produced
发动机燃烧室内反复发生不受控爆炸而发出的重复的砰声、敲击声或类似声响。
A repetitive ping, knock, or similar sound coming from an engine in which there are repeated uncontrolled explosions in the combustion chamber.
The mechanic diagnosed the engine knocking as a result of low-octane fuel.
机械师诊断出发动机爆震是由低辛烷值燃油引起的。
If you hear a persistent knocking from the engine, it may indicate a serious problem.
如果你听到发动机持续发出爆震声，可能表明存在严重问题。
The loud knocking on the door startled everyone in the room.
门上响亮的敲门声惊动了房间里所有人。
常与 at/on 搭配，指明被敲击的对象；此义侧重敲击的动作或声音。
There was a soft knocking on the window.
窗子上有轻轻的敲击声。
knocking 作不可数名词，指听到的敲击声音。若指多次具体的敲击，可用复数 knockings。
We heard knocking from the apartment below.
我们听到楼下的公寓传来敲击声。
此为发动机故障术语，描述气缸内不受控爆炸产生的重复声响，与敲门声无关。
Engine knocking usually means the fuel is burning unevenly.
发动机爆震通常意味着燃油燃烧不均匀。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
敲门声
I heard a knocking at the door, but no one was there.
我听到敲门声，但那里没有人。
敲击声
The machine made a strange knocking sound.
机器发出奇怪的敲击声。
响亮的敲击声
A loud knocking woke everyone in the house.
响亮的敲击声吵醒了屋里的所有人。
发动机爆震
Engine knocking usually indicates a problem with the fuel mixture.
发动机爆震通常表明燃油混合气有问题。
持续不断的敲击声
The persistent knocking on the wall annoyed the neighbors.
持续不断的敲墙声让邻居们很恼火。
敲木头避厄运（祈求好运或避免招来坏事）
I haven't been sick all winter, and I'm knocking on wood.
整个冬天我都没生病，我敲敲木头，但愿别招来祸事。
（机会、麻烦等）降临，出现
When opportunity comes knocking, you need to be ready to open the door.
当机会来临时，你要准备好开门迎接。
接近（某一年龄或某个时间）
Grandpa is knocking on eighty, but he still works in the garden every day.
爷爷快八十岁了，但他每天都还在园子里干活。
这可真是敲门声！
Spoken by the Porter in Shakespeare's Macbeth (Act 2, Scene 3), right after King Duncan is murdered. It is a famous comic line about the knocking at the castle gate, and it is often quoted to show surprise at a sudden loud knocking sound.
出自莎士比亚《麦克白》第二幕第三场，在邓肯王被杀害之后，看门人说出这句著名的喜剧台词，指的是城堡大门传来的敲门声，常被引用以表示突然传来大声敲门时的惊讶。
Use knockings naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
敲门knock加上-ing，联想连续敲击的动作和“咚咚”声；发动机爆震也是这种重复的敲击感，记“knocking=敲个没完”。
语域：mixed 常见场景：日常交谈、车辆维修与机械说明 作名词时通常指敲击的动作或声音，属于日常用语；在汽车或机械语境中常特指发动机爆震或敲缸的异常声响。正式程度视语境而定，多用于口语或技术说明。
不可数名词
Dictionary facts from AI_FALLBACK, ECDICT, WIKTIONARY, WORDNET.