I myself use it for almost everyone, even women. It's just a slang, like "dude". Formally, its a definition for young males, specially teenagers. Male kids and tweens are "meninos" or "rapazinhos", which is diminutive form of "rapaz": it's "little boy".

By definition "Rapaz" is used for a teenagers. But is very common people use this word to a young man.

"Rapaz" is used for kids and teenagers at the north of Spain. (The region or autonomous community is called Asturias). They say " Pedro y Maria tienen dos rapaces". In the rest of the country people dont use that word. We say Pedro y Maria tienen dos niños.

Generally Rapaz is used in many different ways. It can have the translation of " Man " like a slang. " Man, I was thinking that I've done a good deal with the company " In this case, you can use it for young and adults. Rapaz in the sense of a male person can either be used for men between 18-40 years old.

Thank you for that Sophia!