This is the 10459th most frequent Polish word.
czworonożnego
"Four-legged."
The word 'czworonożnym' is used here as an adjective describing 'przyjacielem' (friend) to indicate that the friend is a four-legged animal, specifically referring to the nature of the dog.
Mój pies jest moim najlepszym czworonożnym przyjacielem.
My dog is my best four-legged friend.
In this sentence, 'czworonożnych' is the plural adjective form agreeing with 'towarzyszy' (companions), describing the companions as four-legged, likely referring to pets, through grammatical case agreement in Polish.
Na nasz ranek w parku przyszło kilku czworonożnych towarzyszy.
Several four-legged companions came to our morning at the park.
Here, 'czworonożnego' functions as an adjective modifying the noun 'zwierza' (animal) to describe the animal's characteristic of having four legs, demonstrating the word's descriptive function in creative contexts.