This is the 12758th most frequent Portuguese word.
vaca
Cow.
Here, 'vaca' is used to refer to the animal 'cow'.
Eu vi uma vaca no campo hoje.
I saw a cow in the field today.
Here, 'vaca' is again used to denote the farm animal 'cow'.
Ela tem medo da vaca da fazenda.
She is afraid of the cow at the farm.
In this sentence, 'vaca' may be used in a humorous or casual context referring to a cow.