Synonyms for Nouveau-riche (same or very similar meaning)
WordNet sense 1 (a person who has suddenly risen to a higher economic status but has not gained social acceptance of others in that class):
parvenu, arriviste, upstartWordNet sense 2 (making claim to or creating an appearance of (often undeserved) importance or distinction):
pretentiousFrom the ODE community, based on WordNetadd/edit