25 CFR § 84.002 - What terms must I know?
Encumber means to attach a claim, lien, charge, right of entry or liability to real property (referred to generally as encumbrances). Encumbrances covered by this part may include leasehold mortgages, easements, and other contracts or agreements that by their terms could give to a third party exclusive or nearly exclusive proprietary control over tribal land.
Indian tribe, as defined by the Act, means any Indian tribe, nation, or other organized group or community, including any Alaska Native Village or regional or village corporation as defined in or established under the Alaska Native Claims Settlement Act, which is recognized as eligible for special programs and services provided by the Secretary to Indians because of their status as Indians.
Secretary means the Secretary of the Interior or his or her designated representative.
Tribal lands means those lands held by the United States in trust for an Indian tribe or those lands owned by an Indian tribe subject to federal restrictions against alienation, as referred to Public Law 106-179 as “Indian lands.”