机关枪 

Pinyin: jīguānqiāng 
Meaning：Machine gun   
Sentence：机关枪从隐蔽的阵地开始射击。Machine guns opened up from a concealed position.

More: 

机：

Pinyin: jī 
Meaning: Chance; engine; flexible; machine; occasion; organic; pivot; plane
Radical: 木 
Stokes: 6
Traditional: 機 
Common words/Phrase: 
机器 [jīqì] 【machine; engine】 
飞机 [fēi jī] 【aircraft; aeroplane; plane】
机会 [jīhuì] 【chance; occasion; opportunity】
机能 [jīnéng] 【organic】
机关 [jīguān] 【mechanism】

关： 

Pinyin: guān
Meaning: mountain pass; to close; to shut
Radical: 丷
Stokes: 6
Traditional: 關
Common words/Phrase:
关闭 [guānbì] 【shut】 
关键 [guānjiàn] 【key】
关节 [guānjié] 【joint】
关卡 [guānqiǎ] 【toll-gate】

枪： 

Pinyin: qiāng
Meaning: Spear; rifle; gun
Radical: 木
Stokes: 8
Traditional: 槍
Common words/Phrase:
枪手 [qiāngshǒu] 【gunman】 
枪击 [qiāngjī] 【pop; gun down】
枪杀 [qiāngshā] 【gun down】
枪毙 [qiāngbì] 【executed by shooting】
枪战 [qiāngzhàn] 【gunfight】