This is the 11506th most frequent Polish word.
jeziorem
"Jeziorem" means "lake" (in the instrumental case) in Polish.
The instrumental case 'jeziorem' is incorrectly applied here; the study of context in cases is essential.
Rozmawialiśmy o pięknym jeziorem.
We talked about the beautiful lake.
The word 'jeziorem' is in instrumental case, used here to indicate the means or accompaniment of the action.
Spacerujemy jeziorem o zachodzie słońca.
We are strolling by the lake at sunset.
The word 'jeziorem' might seem to be in instrumental case, but this construction is a mistake; the correct version should use 'jeziorze' in locative case.