The rigorous direct answer is "斌, 文质貌。亦作彬。"(This is a quote 《玉篇》,an authoritative book on language from the 5th century A.D.)
It originally meant "possessing both literary skill and inner qualities". In modern times, it normally means "giving the appearance of courtesy and good breeding". 形容外表和行为斯文有礼。 常用词为"文质彬彬"、"彬彬有礼", 但今天已不写"斌斌"。 楼上黄超说得对,斌字现在通常用作人名。