成语解释：
谓人的心思难以猜测。
成语出处：
清·钱彩《说岳全传》第四回：“虎豹不堪骑，人心隔肚皮。休将心腹事，说与结交知！”
成语例子：
可是，～，有些事儿，哪能想到呢。 ★端木蕻良《曹雪芹》
英文翻译：
different hearts in different breasts—It's hard to tell what's going on in the minds of other people. or People should always be on guard against one another.