Literally, 'non-Aryans.' Dr. Ambedkar makes it clear that he is applying this ancient Vedic term to the aboriginal tribes, who are outside the Caste System. The Laws of Manu says (X,45), "All those tribes in this world, which are excluded from (the community of) those born from the mouth, the arms, the thighs, and the feet (of Brahman) are called Dasyus [slaves], whether they speak the language of the Mlekhhas (barbarians) or that of the Aryans."
Annotation by: Pritchett