Source : Webster's Revised Unabridged Dictionary (1913)

Upstart \Up*start"\, v. i.
   To start or spring up suddenly. --Spenser. Tennyson.

Upstart \Up"start`\, n.
   1. One who has risen suddenly, as from low life to wealth,
      power, or honor; a parvenu. --Bacon.

   2. (Bot.) The meadow saffron. --Dr. Prior.

Upstart \Up"start`\, a.
   Suddenly raised to prominence or consequence. ``A race of
   upstart creatures.'' --Milton.

Source : WordNet®

upstart
     adj : 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)}]
     n 1: an arrogant or presumptuous person
     2: a person who has suddenly risen to a higher economic status
        but has not gained social acceptance of others in that
        class [syn: {parvenu}, {nouveau-riche}, {arriviste}]
     3: a gymnastic exercise performed starting from a position with
        the legs over the upper body and moving to an errect
        position by arching the back and swinging the legs out and
        down while forcing the chest upright [syn: {kip}]