From BrahmaKumaris.Info Encyclopedia
Dada is Hindi for elder brother.
The term is used mainly in connection to the Murli, which BKs believe is the spoken knowledge of God, and the understanding of and experience of Brahma. BKs consider that is difficult to tell which of the two is speaking at any one time, as Brahma is the "mouthpiece" of Shiva, hence the combination of the names. They say Dada Lekhraj, now known as Brahma has become equal to God.
- The combination of Shiva and Brahma, in the subtle world, after Brahma’s ascension in 1969. Raja Yogis go to Mount Abu to meet BapDada through medium.
see also: Avyakt BapDada