When used in this part:

(a) Homestead means the restricted nontaxable lands, not exceeding 160 acres, allotted to an enrolled member of the Osage Tribe pursuant to the act of June 28, 1906 (34 Stat. 539), or the restricted surplus lands designated in lieu thereof pursuant to the act of May 25, 1918 (40 Stat. 578).

(b) Surplus land means those restricted lands, other than the homestead, allotted to an enrolled member of the Osage Tribe pursuant to the act of June 28, 1906 (34 Stat. 539).