This is the 8742nd most frequent Russian word.
петровцы
"Петровцы" refers to "supporters or followers of Peter (often Peter the Great)."
The word 'петровцы' refers to a group of people associated with a person named Petrov, used in the nominative case as the subject of the sentence.
Петровцы пришли на праздник урожая.
The Petrovtsy came to the harvest festival.
Here, 'петровцы' is used in the accusative case ('петровцев'), indicating the group of people being met in the forest.
Мы встретили петровцев в лесу.
We met the Petrovtsy in the forest.
The word 'петровцы' appears in the prepositional case ('с петровцами'), specifying the group of people involved in the conversation.