The phrase "Nouveau riche" is mostly associated with people who are newly rich but lack the refinement or class of old money. In terms of antonyms, we can think of phrases like "old money," "aristocrat," "blue blood," and "establishment." These terms imply that the person's wealth has been in their family for generations, and they have a more sophisticated way of life than those who are newly affluent. Conversely, we can think of "working-class," "middle-class," "lower-income," and "financially struggling" as words that are opposite to "Nouveau riche" as they imply a lack of financial prosperity or in some cases more ethical way of life. Regardless of the antonym, it's essential to recognize that wealth does not always equate to class or decency.