24 C.F.R. § 570.481
(a) Except for terms defined in applicable statutes or this subpart, the Secretary will defer to a state's definitions, provided that these definitions are explicit, reasonable and not plainly inconsistent with the Act. As used in this subpart, the following terms shall have the meaning indicated:
[57 FR 53397, Nov. 9, 1992, as amended at 61 FR 5209, Feb. 9, 1996; 74 FR 36389, July 22, 2009; 80 FR 69871, Nov. 12, 2015]