upstart

Etymology

From Middle English upstarten, upsterten, equivalent to up- + start.

noun

1. One who has suddenly gained wealth, power, or other prominence, but either has not received social acceptance or has become arrogant or presumptuous.
   But electric vehicles and the batteries that made them run became ensnared in corporate scandals, fraud, and monopolistic corruption that shook the confidence of the nation and inspired automotive upstarts. 2006, Edwin Black, chapter 1, in Internal Combustion
   Where the Czech upstart [Lukáš] Rosol, ranked 100 in the world, all but blew [Rafael] Nadal's head off with his blunderbuss in a fifth set of unrivalled intensity on Thursday night, [Julien] Benneteau, a more artful citizen, used a rapier to hurt his vaunted foe before falling just short of a kill. In the end, it was he who staggered from the scene of the fight. 29 June 2012, Kevin Mitchell, “Roger Federer back from Wimbledon 2012 brink to beat Julien Benneteau”, in The Guardian, archived from the original on 2016-11-15
2. The meadow saffron.

adj

1. Acting like a parvenu.
2. self-important and presumptuous.

verb

1. to rise suddenly, to spring