This is the 8237th most frequent Polish word.
ostałowski
The word "ostałowski" does not exist in Polish. It might be a typo or a proper noun.
In this sentence, 'Ostałowski' is used as a proper surname.
Pan Ostałowski był naszym przewodnikiem po muzeum.
Mr. Ostałowski was our guide at the museum.
Here, 'ostałowski' is used as an adjective derived from a surname, possibly describing a shade characteristic or resembling something associated with Ostałowski.
W tego rodzaju drewnie znajduje się ostałowski odcień szarości.
In this type of wood, one finds an Ostałowski shade of gray.
In this case, 'ostałowskiego' refers to a possessive form of a residence or something belonging to or associated with Mr. Ostałowski.