Bada is Hindi for big or elder. Bhaiya is used to address a 'bhai', a brother. Hence, Bade Bhaiya [Devnagari:बड़े भैया, Also spelled as 'bade bhaiyya', 'bade bhaiyaa' etc.] is Hindi for Elder Brother.
Bade Bhaiya is an upcoming Salman Khan movie to be directed by Sooraj Barjatya, who has earlier made Maine Pyar Kiya, Hum Aapke Hain Kaun, and Hum Saath Saath Hain, the latter two featuring Salman as the younger brother in the family while Mohnish Behl played the elder one.
This time, after a long break with Barjatya, Salman is reported to be the elder brother, hence playing the title role, while Arjun Kapoor is reported to be playing the younger.