Any construction, whether a temporary breastwork or permanent fortification, for attack or defense, the material of which is chiefly earth. [1913 Webster]
The operation connected with excavations and embankments of earth in preparing foundations of buildings, in constructing canals, railroads, etc. [1913 Webster]

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OXFORD DICTIONARY

earthwork, n.
1 an artificial bank of earth in fortification or road-building etc.
2 the process of excavating soil in civil engineering work.

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THESAURUS

earthwork

abatis, advanced work, arch dam, backstop, balistraria, bamboo curtain, bank, banquette, bar, barbed-wire entanglement, barbican, barrage, barricade, barrier, bartizan, bastion, battlement, bear-trap dam, beaver dam, boom, breakwater, breastwork, brick wall, buffer, bulkhead, bulwark, casemate, cheval-de-frise, circumvallation, cofferdam, contravallation, counterscarp, curtain, dam, defense, demibastion, dike, ditch, drawbridge, embankment, enclosure, entanglement, escarp, escarpment, fence, fieldwork, fortalice, fortification, gate, glacis, gravity dam, groin, hydraulic-fill dam, iron curtain, jam, jetty, leaping weir, levee, logjam, loophole, lunette, machicolation, mantelet, merlon, milldam, moat, mole, mound, outwork, palisade, parados, parapet, portcullis, postern gate, rampart, ravelin, redan, redoubt, roadblock, rock-fill dam, sally port, scarp, sconce, seawall, shutter dam, stockade, stone wall, tenaille, vallation, vallum, wall, weir, wicket dam, work

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