In this subchapter:
((1)) ** BIA** The term “BIA” means the Bureau of Indian Affairs.
((2)) ** Department** The term “Department” means the Department of the Interior.
((3)) ** Secretary** The term “Secretary” means the Secretary of the Interior.
((4)) ** Under Secretary** The term “Under Secretary” means the Under Secretary for Indian Affairs established under .section 5633(a) of this title