вы́скочка — meaning in English

vyskochka

English meaning

parvenu noun Someone who has moved up into a higher social class, usually by becoming rich or powerful, but who is not fully accepted by that class.
upstart noun Someone who has suddenly risen to wealth, power, or status and hasn't yet earned proper social acceptance, or who acts arrogant about it.
vulgarian noun A person whose manners or taste are crude or tasteless, especially someone who does not notice it in themselves.

вы́скочка is used for these senses in English:

nouveau riche (pejorative) New money; wealthy persons whose fortunes are newly acquired, and who are therefore perceived to lack the refinement of those who were raised wealthy.
parvenu A person who has risen, climbed up, or has been promoted to a higher social class, especially through acquisition of wealth, privileges, or political authority but has not gained social acceptance by those within that new class.
upstart One who has suddenly gained wealth, power, or other prominence, but either has not received social acceptance or has become arrogant or presumptuous.
vulgarian A vulgar individual, especially one who emphasizes or is oblivious to his or her vulgar qualities.

noun Someone who has suddenly risen to wealth, power, or status and hasn't yet earned proper social acceptance, or who acts arrogant about it.
adj Acting self-important or presumptuous, especially given a short time in a position.