This is the 3037th most frequent Polish word.
piłkarski
"Piłkarski" means "related to football (soccer)."
Here, 'piłkarski' serves as an adjective to illustrate the type of equipment, which is for football.
Kupiliśmy nowy sprzęt piłkarski dla drużyny.
We bought new football equipment for the team.
The word 'piłkarski' is used here as an adjective describing the fan, relating him to football.
Mój brat jest zapalonym kibicem piłkarskim.
My brother is a passionate football fan.
In this sentence, 'piłkarski' describes the kind of match, specifically indicating that it is related to football.