This is the 3515th most frequent Polish word.
świetnej
The Polish word "świetnej" means "great" or "excellent" (feminine, genitive or dative case).
Here, 'świetnej' is an adjective in the genitive form ('świetnej jakości') modifying 'quality', describing excellence.
To była świetnej jakości sukienka.
It was a dress of excellent quality.
In this sentence, 'świetnej' is used as an adjective in the genitive form ('świetnej organizacji') that modifies 'organization', indicating its excellence.
Rozmawiałem z świetnej organizacji członkami.
I talked with members of an excellent organization.
Here, 'świetnej' serves as an adjective in the genitive form ('świetnej książki') modifying 'book', indicating the book's high quality or greatness.