Heart in one's mouth:

心在某人的嘴巴里 ×

非常緊張；提心吊膽；害怕之極 √

例句：

When the bear came out of the woods towards us, our hearts were in our mouths.

當(dāng)熊從樹叢中朝我們走來時(shí)，我們的心都快跳出來了。

Put words into one's mouth:

將話塞進(jìn)某人的嘴巴里 ×

無根據(jù)地說某人說過某些話 √

例句：

Stop putting words into my mouth!

不要再無根據(jù)地說我的瞎話了！

Run off at the mouth:

從嘴巴流出來 ×

信口開河 

例句：

Don't trust him. He always runs off at the mouth.

不要相信他，他經(jīng)常信口開河。