► 名詞 兄さん [(1)にいさん] [coll] [男] meaning:brotherrank:3 ☆ 兄さん! ⇨ Big brother! (☛ Often used to address a man senior to you in family (or a family-like group), regardless of blood relations)
More examples:
彼のお兄さんは有名な野球選手だ ⇨ His brother is a famous baseball player