This is the 5643rd most frequent Polish word.
wiosnę
"Spring" (the season).
The word "wiosnę" is in the accusative case as it is the direct object of the verb "czekam" (I am waiting).
Czekam na wiosnę, ponieważ kocham, gdy kwitną kwiaty.
I am waiting for the spring because I love it when flowers bloom.
The word "wiosnę" appears in the accusative case here to emphasize the season as the object of the verb "lubią" (they like).
Wiosnę najbardziej lubią ci, którzy pasjonują się ogrodem.
Spring is most loved by those who are passionate about gardening.
Here, "wiosnę" is in the accusative case, depicting what the subject ("I") can already feel (direct object of the verb "czuję").