- [countable]
a tool with a handle and a heavy metal head, used for breaking things or hitting nails 锤子；榔头 
a gentle tap with a hammer 用锤子轻轻敲打 He struck her on the head with a hammer. 他用锤子敲她的头。
Oxford Collocations Dictionaryverb + hammer- hit something with
- tap something with
- use
- …
- blow
- a hammer and chisel
- a hammer and nails
- hammer and sickle
- …
- [countable]
a tool with a handle and a wooden head, used by a person in charge of an auction (= a sale at which things are sold to the person who offers the most money) in order to get people’s attention when something is just being sold （拍卖用的）木槌 to come/go under the hammer (= to be sold at auction) 被拍卖 Forty modern Russian paintings went under the hammer at Christie’s today. 四十幅现代俄罗斯油画今天在佳士得拍卖。
- [countable]
a small wooden part inside a piano, that hits the strings to produce a sound 音槌 - [countable]
a part inside a gun that makes the gun fire 击铁 - [countable]
a metal ball attached to a wire, thrown as a sport 链球 - often the hammer[singular]
the event or sport of throwing the hammer 掷链球（运动） 
tool工具
in piano钢琴
in gun枪炮
sport体育运动
Word OriginOld English hamor, hamer, of Germanic origin: related to Dutch hamer, German Hammer, and Old Norse hamarr ‘rock’. The original sense was probably ‘stone tool’.
Idioms
hammer and tongs
- (informal)
if two people are at it hammer and tongs or go at it hammer and tongs, they argue or fight with a lot of energy and noise 激烈争吵（或打斗） We could hear the neighbours going at it hammer and tongs. 我们可以听到邻居在激烈地争吵。