A material entity that is (1) a bona fide or fiat object part of the crust, any bodies of liquid on or contained within the crust, or planetary boundary layer (if present) of a terrestrial planet (including Earth), dwarf planet, exoplanet, natural satellite, planetesimal, or small Solar System body, and that (2) overlaps the planetary surface (including having a boundary that coincides with part of the planetary surface).