in one ear and out the other意思是“一只耳朵进，另一只耳朵出”，也就是我们常说的“左耳朵进，右耳朵出”，比喻不把别人的话放在心上。

【例句】
I have to remind my students a dozen times to copy down their homework—it's like in one ear and out other.
学生们听话似乎总是左耳朵进右耳朵出，我不得不数次提醒他们把家庭作业抄下来。

You can try to convince him, but with him it's usually in one ear and out the other.
你可以尝试说服他，不过他听话经常左耳朵进右耳朵出。