This is the 5258th most frequent Polish word.
rowerem
"Rowerem" means "by bike" or "by bicycle" in English.
Here, 'rowerem' acts as an instrumental case denoting the means of transportation used, which is 'by bicycle'.
Jechałem rowerem do sklepu.
I rode the bicycle to the store.
In this context, 'rowerem' indicates the mode of travel, specifying it as 'by bicycle' in the instrumental case.
Podróżowaliśmy po górskich ścieżkach rowerem.
We traveled through mountain trails by bicycle.
Here, 'rowerem' is used in the instrumental case to describe the method of the trip ('by bicycle').