/in"fil'/ , v.t.
1. to fill in: The old stream beds have been infilled with sediment.
n.
2. the planned conversion of empty lots, underused or rundown buildings, and other available space in densely built-up urban and suburban areas for use as sites for commercial buildings and housing, frequently as an alternative to overdevelopment of rural areas.
adj.
3. of, pertaining to, or involving the use of infill in urban planning: infill condominium projects; infill office buildings and retail space.
Also, in-fill .
[ 1875-80; IN- 1 + FILL ]