NOT DO somethingsomething that you must not do because it is considered to be unacceptablebehaviour 不准干的事;不能接受的事
Colouring your hair was a no-no at that time.
染发在那时是绝不允许的。
Examples from the Corpus
no-no• Earrings and heavychains around the neck are a no-no on the field.• Handwritten signs in the restaurant are a no-no.• The use of fresh ground beef is a no-no.• Apparently, this is a no-no in insurance land.• In technicalterms, this is a big no-no.• And crying for me was a big no-no in business life.• A word of warning, though-counters are generally considered a designno-no.• There is lots of touching, and I think touching, in our society, is a realno-no.