This is the 10287th most frequent German word.
portimao
"Portimão" is not a German word; it is the name of a city in Portugal.
Here, 'Portimão' is used as a proper noun to refer to a specific city in Portugal.
Portimão ist eine wunderschöne Stadt in Portugal.
Portimão is a beautiful city in Portugal.
In this sentence, 'Portimão' functions as a proper noun indicating the location where the action took place.
Letztes Jahr habe ich in Portimão Urlaub gemacht.
Last year, I vacationed in Portimão.
This usage of 'Portimão' refers to the city highlighting its characteristic features, in this case, the beaches.