no-no

1. N-SING If you say that something is a no-no, you think it is undesirable or unacceptable. 不準(zhǔn)干的事; 不能接受的事物[非正式] ['a' N]

We all know that cheating on our taxes is a no-no. 我們都知道偷稅漏稅是絕對不行的。