Prabhu

Prabhu master; lord. Prabhu was traditionally used as a title for Sri Guru and for the Supreme Lord (esp. Mahaprabhu, Nityananda Prabhu, and Advaita Prabhu). Srila Bhakti Siddhanta Saraswati Thakur started the practice of referring to his disciples as Prabhu because he saw them as extensions of his Gurudev, and he also encouraged his disciples to adopt this practice. Thus Prabhu is used within the Saraswat Gaudiya–Vaisnava sampradaya as a respectful address for initiated, male devotees of all ages, with the exception of sannyasis.

— books Sri Sri Prema-vivarta / Glossary