This is the 4985th most frequent Polish word.
policją
"Policją" means "police" in English, used in the instrumental case.
Here, "policją" is used in the instrumental case to indicate the entity (the police) with which the action (speaking) was performed.
Rozmawiałam wczoraj z policją o incydencie.
I spoke with the police yesterday about the incident.
In this sentence, "policją" is part of the prepositional phrase indicating the agent (the police) performing the action of stopping.
Zostałem zatrzymany przez policję na ulicy.
I was stopped by the police on the street.
Here, "policją" is used in the instrumental case following the verb "spotkałem się," indicating the group (the police) involved in the meeting.