This is the 10084th most frequent Polish word.
białaczek
The word "białaczek" does not exist in standard Polish; it may be a misspelling or misconstruction.
The word 'białaczek' here refers to a type of white butterfly.
Lubię obserwować białaczek w lesie.
I like observing white butterflies in the forest.
In this sentence, 'białaczek' indicates the subject, which is the butterfly.
Na zdjęciu widzisz białaczek na kwiatku.
In the picture, you see a white butterfly on a flower.
'Białaczek' in this context refers generically to species of butterflies of white coloration.