1.
N-COUNT
If there is a boom in the economy, there is an increase in economic activity, for example, in the number of things that are being bought and sold. (经济) 繁荣
例：
An economic boom followed, especially in housing and construction.
接着是一个经济的繁荣，尤其在住房和建筑方面。
例：
The 1980s were indeed boom years.
20世纪80年代确实是繁荣的时代。
2.
N-COUNT
A boom in something is an increase in its amount, frequency, or success. 增长
例：
The boom in the sport's popularity has meant more calls for stricter safety regulations.
该项运动普及程度的大幅提高带来了更多要求更严格安全法规的呼声。
3.
V-I
If the economy or a business is booming, the number of things being bought or sold is increasing. 激增
例：
By 1988 the economy was booming.
到1988年为止经济一直很繁荣。
例：
Sales are booming.
销售量在激增。
4.
V-T/V-I
When something such as someone's voice, a cannon, or a big drum booms, it makes a loud, deep sound that lasts for several seconds. 发出低沉洪亮的声音
例：
"Ladies," boomed Helena, without a microphone, "we all know why we're here tonight."
“女士们”，海伦娜没用话筒朗声说道，“我们都知道今晚我们为什么在这儿。”
例：
Thunder boomed over Crooked Mountain.
雷声在克鲁克德山上空轰鸣。
5.
PHRASAL VERB
Boom out means the same as . 发出低沉洪亮的声音
例：
Music boomed out from loudspeakers.
扬声器传出了低沉响亮的音乐。
例：
A megaphone boomed out, "This is the police."
扩音器传出了低沉而响亮的声音：“我们是警察。”
6.
N-COUNT/SOUND
Boom is also a noun. 轰鸣声
例：
The stillness of the night was broken by the boom of a cannon.
夜晚的寂静被大炮的轰鸣声打破了。