"Nono" is a slang term for "no" or "don't do it." There are several synonyms for this term that can be used in different contexts. These synonyms include "negative," "not okay," "unacceptable," "forbidden," "undesirable," "unwanted," "unsuitable," "improper," "inadvisable," and "ill-advised." In informal settings, other slang synonyms for "nono" include "nah," "nope," "not on," "no way," "not good," "not happening," and "not cool." It is important to use the appropriate synonym depending on the context and the audience to convey the right message effectively.