From Hindupedia, the Hindu Encyclopedia

By Jit Majumdar

  1. the realm of Brahmā; the realm of the Infinite
  2. one of the celestial realms or planes of existence in Hindu cosmology, which is the abode of those spirits who have achieved the highest state of liberation. In Theravāda Buddhism, it includes the 20 uppermost planes of existence, of which the lower 16 of are the rupa-brahma-loka, i.e., realms which are made of and inhabited by existences having name and form – each realm in ascending order being inhabited by progressively radiant gods. The highest four realms, the arupa-brahma-loka, are devoid of any substance, and any relative quality like name and form.