That's a formal way to say "older brother". But younger girls call the older brother/guy/friend "oppa" They add "oppa" when they say their name.

oppa means ' older brother'. younger sister says their, or almost older man 'oppa'. oppa=오빠=older man,brother.

Tee hee. I've heard opa means "grandfather" in Dutch. Don't be puzzled, they're interested in getting along with you if younger girls call that.