Nouveau riche

Nouveau riche (French for "new rich"), or new money refers to persons who acquire wealth within their generation. It is generally used to emphasize that the persons were previously part of a lower economic or social class, and that the acquisition of wealth has provided the ability to do or to have things that were previously out of their reach.

The term can also be used in a derogatory fashion, for the purposes of social class distinction, to describe persons with newfound wealth and who are viewed as lacking the experience, finesse, or taste to use wealth in the same manner as old money - persons from families who have been wealthy for multiple generations. The implication is that, despite their wealth, they are still of lower- or middle-class origin, and therefore culturally inferior. A stereotypical example would be persons with new wealth who spend money conspicuously, aspire to the tastes of their betters, or fail to disguise lower class preference.

Some linguistic prescriptivists teach that as nouveau riche is a foreign word in English, it is pluralized nouveaux riches, and should be italicized when appearing in print.

source:
http://en.wikipedia.org/wiki/Nouveau_riche