Never mention it to outsiders.

这件事别跟外人说。

《新英汉大辞典》

A lot of the jargon they use is unintelligible to outsiders.

他们所用的大量行话是外人听不懂的。

《牛津词典》

The Cantonese accent also seems strange to outsiders.

对外来者而言，当地的粤语口音也显得很古怪难懂。

youdao

There is no independent confirmation of the tolls, and the region has been closed to outsiders.

VOA: standard.2009.10.28

You answered that you majored in course 2. It sounds like a secret code to outsiders.

你刚才回答你的专业是课程2。这在外人听起来就像是秘密代码一样。

MIT用数字说话 - SpeakingMax英语口语达人

The feeling is that the establishment of a new native Egyptian dynasty might have led to the enslavement of any remaining Semites or Semitic outsiders, and that would include, of course, the Hebrews.

一个新的埃及王朝建立,这将会导致所有剩余的闪族人被迫为奴,或者是闪族之外的人，当然也包括希伯来人。

耶鲁公开课 - 旧约导论课程节选

It's closed to outsiders, but Hewlett-Packard Co. is staging the greatest new show in corporate America.

FORBES: All Carly, all the time

Unlike the inhabitants of Yorkshire, Lutonians do not talk up their home to outsiders.

ECONOMIST: How to persuade people to love their town

The latter, who wanted to cash out, threatened to sell her stake to outsiders.

FORBES: Monsieur Big