An example of a no no is eating cookies before dinner after your mom said not to eat them.
Smoking indoors is becoming a real no-no these days, in many places.
He threw two no-nos in his career.
It's a no-no because defense attorneys are all over any hint of psychic involvement.
Financial troubles at the start of your married life are a big no-no.
You do not have to stick to this slavishly but it might help you avoid an acknowledged no-no.
And it was somewhere during this last leg of our trek that to be a Doctor Who viewer became a social no-no.