This is the 4152nd most frequent Polish word.
busa
The Polish word "busa" is not a standard word but might be an informal or regional variation meaning "bus" (a large vehicle for transporting people).
In this sentence, 'busa' refers to a 'bus' in its instrumental case, as it's used after the verb 'jechać' in Polish.
Wczoraj jechałam busem do pracy.
Yesterday, I took a bus to work.
Here, 'busa' is in the genitive case to express location in relation to the noun 'bus'.
Zobaczyłam plakaty na bocznej ścianie busa.
I saw posters on the side wall of the bus.
In this case, 'busa' is in the genitive case used to denote possession or spatial relationship.