infill

in·fill  (nfl)

n.

1. The use of vacant land and property within a built-up area for further construction or development, especially as part of a neighborhood preservation or limited growth program.

2. A substance or material used to fill in: a steel structure with an infill of redwood sheathing.

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In cartography, the filling of an area or feature with color, e.g., roads, town shapes, lakes, etc.