This is the 15113th most frequent Polish word.
rzepakowego
"Rzepakowego" means "of or relating to rapeseed."
The word 'rzepakowy' is used here as an adjective describing the type of oil, indicating it is made from rapeseed.
Olej rzepakowy jest zdrowy dla naszego serca.
Rapeseed oil is healthy for our heart.
In this sentence, 'rzepakowe' modifies 'kwiaty' to specify the type of flowers—those of rapeseed plants.
Na polach wiosną zakwitają kwiaty rzepakowe.
In spring, rapeseed flowers bloom in the fields.
Here, 'rzepakowemu' is used in the instrumental case as an adjective modifying 'olejowi,' showing the noun's role in the sentence.