The Collaborative International Dictionary of English v.0.48:

Parvenu \Par"ve*nu`\, n. [F., prop. p. p. of parvenir to attain
   to, to succeed, to rise to high station, L. pervenire to come
   to; per through + venire to come. See Par, prep., and
   Come.]
   An upstart; a man newly risen into notice.
   [1913 Webster] Parvis

WordNet (r) 3.0 (2006):

parvenu
    adj 1: characteristic of someone who has risen economically or
           socially but lacks the social skills appropriate for this
           new position [syn: nouveau-riche, parvenu,
           parvenue, upstart(a)]
    2: of or characteristic of a parvenu [syn: parvenu,
       parvenue]
    n 1: a person who has suddenly risen to a higher economic status
         but has not gained social acceptance of others in that
         class [syn: upstart, parvenu, nouveau-riche,
         arriviste]