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back-fill
back-fill v. 
/ˈbakfɪl/,
Brit. /ˌbakˈfɪl/
, /ˌbakˈfɪl//ˈbakfɪl/U.S. /ˈbækˌfɪl/
(1651 in Dict. Older Sc. Tongue)/ˈbækˌfɪl/ΘΚΠ
society > occupation and work > industry > earth-moving, etc. > [verb (transitive)] > fill in earth
to cover in1819
back-fill1930
1930 Engineering 29 Aug. 259/2 The trenches have to be backfilled with sand, gravel or other good clean earth.
1955 Archit. Rev. 118 393/3 Mineral operators, when they have finished extraction, are generally free to backfill without planning consent.
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