Honorific term for one's own or someone else's older brother. Used both to address and to refer to an older brother politely.
See also: 兄さん
お兄さんは大学生ですか。
Is your older brother a university student?
お兄さん、ちょっと手伝ってくれる？
Hey big brother, can you help me a bit?
Familiar, often vocative term for a young man whose name one does not know, similar to 'buddy' or 'young man'. Used in casual, friendly address.
See also: 兄さん
そこのお兄さん、ちょっと道を教えてくれませんか。
Hey there, young man, could you tell me the way?
あのお兄さん、いつも元気だね。
That fella is always so energetic, isn't he.
He looks a lot like his older brother.
Excuse me, sir, is this the right way?
お兄さん is the polite, friendly way to refer to an older brother or young man, whereas 兄貴 is rougher and more familiar in tone.