Definition from Wiktionary, the free dictionary
- (colloquial, often childish) Something that is forbidden, prohibited, discouraged or taboo.
- Smoking indoors is becoming a real no-no these days, in many places.
- (baseball, colloquial) A no-hitter; a game in which no batter on one of the teams got a hit.
- He threw two no-nos in his career.
- (something forbidden, ...): must