From Longman Dictionary of Contemporary Englishinfillin‧fill /ˈɪnfɪl/ noun [uncountable] especially British English 1 something that is used to fill a space infill panels2 the process of filling a space, especially by building new houses infill developments —infill verb [intransitive, transitive]From Longman Business Dictionaryinfillin‧fill /ˈɪnfɪl/ noun [uncountable] especially American English PROPERTY when new homes and other buildings are built in between the buildings that are already there, rather than around their edgeInfill is encouraged in areas like Tuscon, which has vast amounts of vacant land within the city limits.
