This is the 16882nd most frequent Polish word.
wynajmowanej
"Rented" or "being rented."
In this sentence, "wynajmowanej" is the genitive singular feminine form of the past participle "wynajmowana," referring to an apartment being rented by someone.
Odwiedziłem mieszkanie wynajmowanej przez studentów.
I visited the apartment rented by the students.
Here, "wynajmowanej" describes the feminine noun "chacie" in the locative case, showing the place where we're staying.
Spędzamy wakacje w wynajmowanej chacie w górach.
We are spending our vacation in a rented cabin in the mountains.
In this instance, "wynajmowanej" refers to the car (a feminine noun "samochodu"), indicating it has been rented from someone.