Oppa 오빠 = a male older than a female / older brother to a female / a way a female tries to get attention from a male they like (my interpretation) deul 들 = plural Thus, 오빠들 (oppa deul) means older brothers to a female or when a female refers to males older than she. I believe this could be said by a female fan to some male popular artists/ boy group members in South Korea.