This is the 12587th most frequent Polish word.
nastoletnia
"Teenage" or "teenaged" (feminine form).
Used as an adjective describing a girl in her teenage years.
Nastoletnia dziewczyna siedziała na ławce w parku.
The teenage girl was sitting on the bench in the park.
Used as an adjective in a feminine form modifying the noun 'person.'
Jej zachowanie było typowe dla osoby nastoletniej.
Her behavior was typical for a teenage person.
Used as an adjective describing the phrase 'person' emphasizing the state of being in adolescence.