This is the 8076th most frequent Russian word.
купянска
"Купянска" does not have a standalone meaning in Russian; it likely refers to "Купянск," the name of a town in Ukraine.
Here 'Купянска' denotes a location genitive case form, indicating 'of Kupiansk'.
Я купил книгу в городе Купянска.
I bought a book in the city of Kupiansk.
In this sentence 'Купянска' is used in the genitive case, specifying the origin of departure.
Он уехал из Купянска вчера.
He left Kupiansk yesterday.
'Купянска' is again in the genitive case, showing possession or relation, used to describe the district.