Korean word "오빠" "oppa" It means your "older(elder) brother" or "familiar older guy" like "brother"->"bro" but "oppa" be used(said) by women. If were a man say "oppa", he seems to be gay. -_- similar word is "오라버니" "or-a-bor-ni" , "오라버니" is an honorific and classical expression. so almost everyone use "oppa" tip woman -> (elder)man : "오빠" woman -> (elder)woman : "언니" man -> (elder)man : "형" man -> (elder)woman : "누나" :)) My friend dudujon thought me that. And i hope it'll help you too.

There's a very good explanation in this post by 쌤: http://www.italki.com/entry/437405