inholding

Etymology
From.

Noun

 * 1) A piece of privately-owned land inside the boundary of a national park, national forest, state park, or similar publicly-owned protected area.

Usage notes
Note that the inholder can be another government agency. Per 43 CFR Subtitle A (10-1-09 Edition) p. 527: Inholding means State-owned or privately owned land, including subsurface rights of such owners underlying public lands or a valid mining claim or other valid occupancy that is within or is effectively surrounded by one or more areas.