2个回答
Keep It down 有两个意思：
1. 小声点 别这么喧哗 （和 keep quiet 有相同意思）
例句： Keep it down, I am trying to study.
2. 吃得下去 没有呕吐
通常以反义方式来用，比如
He has an upset stomach. He just can't keep anything down.
他肠胃不舒服，吃什么吐什么
keep down 保持，控制
they are taking steps to keep down the rabbit population.
他们采取步骤控制兔子的繁殖增长。