1. 刀
    A knife is a tool for cutting or a weapon and consists of a flat piece of metal with a sharp edge on the end of a handle.

    e.g. ...a knife and fork...
           一副刀叉
    e.g. Two robbers broke into her home, held a knife to her throat and stole her savings.
           两个盗贼闯进了她的家，把刀架在她的脖子上，抢走了她的积蓄。

2. 用刀伤害
    To knife someone means to attack and injure them with a knife.

knife在线翻译

    e.g. Dawson takes revenge on the man by knifing him to death...
           道森用刀杀死了他的仇人。
    e.g. She was knifed in the back six times.
           她的背部中了6刀。

3. 手术刀
    A surgeon's knife is a piece of equipment used to cut flesh and organs during operations. It is made of metal and has a very thin sharp edge.

4. 接受手术；动手术
    If you go under the knife, you have an operation in a hospital.

    e.g. Kelly was about to go under the knife when her surgeon stopped everything.
           凯莉的手术就要开始时被她的外科医生给叫停了。

5. see also: carving knife;fish knife;flick knife;palette knife;paper knife;pocket knife;Stanley knife

6. 轻而易举；毫无困难
    If someone does something like a knife through butter or like a hot knife through butter, they do it very easily.

knife

    e.g. Spending by Japanese companies has left them more competitive than companies in other nations. They will be cutting through the competition like a hot knife through butter.
           日本公司的支出使得它们比其他国家的公司更具竞争力。它们将在竞争中轻而易举地取胜。

7. （紧张的气氛）使人透不过气来
    If you have been in a place where there was a very tense atmosphere, you can say that you could have cut the atmosphere with a knife.

    e.g. Officials hung the flag upside down. You could have cut the atmosphere with a knife.
           官员们把旗子挂倒了。气氛紧张得让人透不过气来。

8. 对…磨刀霍霍；对…兴师问罪
    If a lot of people want something unpleasant to happen to someone, for example if they want them to lose their job, you can say that the knives are out for that person.

    e.g. The Party knives are out for the leader.
           该党派要向其领导人开刀了。

9. 落井下石；往伤口上撒盐
    If you twist the knife or if you turn the knife in someone's wound, you do or say something to make an unpleasant situation they are in even more unpleasant.

    e.g. Travis twisted the knife by laughing at her...
           特拉维斯火上浇油般地嘲笑她。
    e.g. It is the turn of Latvia to twist the knife.
           轮到拉特维亚落井下石了。