This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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v. Third-person singular simple present indicative form of upstart.

"I generally fly on major carriers -- one of the things that's really distinguished old-school airlines like United (which I usually fly) from the upstarts is that loyalty is rewarded."

pretentious   

upstarted    upstarting    upstarts   

gymnastic exercise   

parvenu    mushroom    start-up    nouveau riche    arriviste   

interloper    usurper    brat    scoundrel    rabble