surface density
the density of a two-dimensional object, or of the surface of a three-dimensional object, calculated as the mass per area
en-US/ˈsɝfɪs ˈdɛnsɪti/
en-GB/ˈsɜːfɪs dɛnsɪtiː/
the density of a two-dimensional object, or of the surface of a three-dimensional object, calculated as the mass per area