/nɒk ||; nɑk/verb1 [I] knock (at/on sth) to make a noise by hitting sth firmly with your hand 敲: Someone is knocking at the door. 有人在敲门。I knocked on the window but she didn't hear me. 我敲了敲窗，可是她没有听见。
2 [T] knock sth (on/against sth) to hit sb/sth hard, often by accident 敲，击，碰（往往是出于偶然的）: He knocked the vase onto the floor. 花瓶给他一碰掉到地板上。Be careful not to knock your head on the shelf when you get up. 站起来的时候，小心别把头碰到架子上。to knock sb unconscious 把某人打晕
3 [T] (informal 非正式) to say bad things about sb/sth; to criticize sb/sth （用言辞）攻击，批评
knock on wood→
WOOD(
informal 非正式) to be in a place; to travel and live in various places 在某个地方；漫游；漂泊:
Is last week's newspaper still knocking about? 上个星期的报纸是不是还在什么地方？ knock sb down to hit sb causing him/her to fall to the ground 击倒；撞倒:
The old lady was knocked down by a cyclist. 这个老太太被骑自行车的撞倒了。 knock sth down to destroy a building, etc 拆毁（建筑物等）:
They knocked down the old factory because it was unsafe. 那家旧工厂不安全，所以他们把它拆了。 knock off (sth)(
spoken 口语) to stop working 停止工作:
What time do you knock off? 你什么时候下班？ knock sth off 1 (informal 非正式) to reduce a price by a certain amount 降价: He agreed to knock £10 off the price. 他同意减价10英镑。
2 (slang 俚语) to steal sth 偷
knock sb out 1 to hit sb so that he/she becomes unconscious or cannot get up again for a while 击晕；击倒: The punch on the nose knocked him out. 那一拳打在他鼻子上，把他打晕了。
2 (used about a drug, alcohol, etc) to cause sb to sleep （指毒品、酒等）使人入睡
knock sb out (of sth) to beat a person or team in a competition so that they do not play any more games in it （比赛中）淘汰某人:
Belgium was knocked out of the European Cup by France. 比利时队在欧洲杯大赛中被法国队淘汰出局。 knock sb/sth over to cause sb/sth to fall over 使某人或某物翻倒:
Be careful not to knock over the drinks. 小心别把饮料打翻。