This is the 7761st most frequent Polish word.
marcina
"Marcina" is the feminine form of the name Martin (Marcin) in Polish.
Here, 'Marcin' is a proper noun, the name of a person.
Marcin kupił nowy samochód.
Marcin bought a new car.
In this sentence, 'Marcina' is the accusative form of the proper noun 'Marcin', showing that Marcin is the direct object of the verb 'spotkałem'.
Spotkałem dzisiaj Marcina.
I met Marcin today.
Here again, 'Marcina' is in the accusative case because it is the direct object of the verb 'nie widziałem'.