This is the 11623rd most frequent Polish word.
kiszonej
"Pickled."
The word 'kiszonej' is used as an adjective describing 'kapusty' (cabbage) indicating that it has been pickled.
Uwielbiam smak kiszonej kapusty.
I love the taste of pickled cabbage.
Here, 'kiszonej' modifies 'kapusty,' specifying the ingredient of the soup.
Na lunch zjedliśmy zupę z kiszonej kapusty.
For lunch, we ate soup made with pickled cabbage.
In this sentence, 'kiszonej' again describes 'kapusty,' emphasizing its pickled quality in a nostalgic context.