Adi Dharm refers to the religion of Adi Brahmo Samaj the first development of Brahmoism and includes those Sadharan Brahmo Samajists who were reintegrated into Brahmoism after the 2nd schism of 1878 at the instance of Hemendranath Tagore. This was the first organised casteless movement in British India and reverberated from its heart of Bengal to Assam, Bombay State (modern Sindh, Maharastra and Gujarat), Punjab and Madras, Hyderabad, Bangalore.
Read more about Adi Dharm: Tenets, Founders of Adi Dharma, Genesis of Adi Dharma