This is the 3685th most frequent Portuguese word.
vacas
"Cows."
Here, 'vacas' refers to the animal, cows, used in a traditional agricultural context.
As vacas pastam no campo verde.
The cows graze in the green field.
In this sentence, 'vacas gordas' is used idiomatically to represent 'prosperous times,' referring to the biblical phrase representing wealth.
Ele abriu uma conta em vacas gordas.
He opened a savings account during prosperous times.
The word 'vacas' is used to generally denote cows within an economic context related to livestock farming.