This is the 12374th most frequent Polish word.
muchomorów
The Polish word "muchomorów" means "of toadstools" or "of fly agarics" (genitive plural form).
Here, "muchomorów" is the genitive plural form, used because the verb "znalazłem" (found) selects this grammatical case for its object in Polish.
W lesie znalazłem kilka muchomorów.
In the forest, I found a few toadstools.
In this sentence, "muchomorów" is in the genitive plural form, required after the verb "boję się" (am afraid of).
Boję się muchomorów, bo są trujące.
I am afraid of toadstools because they are poisonous.
Here, "muchomorów" is in the genitive plural form, used because the noun "grupę" (group) which it qualifies has this case due to the prepositioned action.