To cut; to form or shape by cutting; to make by incision, hewing, or the like. [1913 Webster]
"The wide wound that the boar had trenched
In his soft flank." [1913 Webster]

"This weak impress of love is as a figure
Trenched in ice, which with an hour's heat
Dissolves to water, and doth lose its form." [1913 Webster]
To fortify by cutting a ditch, and raising a rampart or breastwork with the earth thrown out of the ditch; to intrench. Pope. [1913 Webster]
"No more shall trenching war channel her fields." [1913 Webster]
To cut furrows or ditches in; as, to trench land for the purpose of draining it. [1913 Webster]
To dig or cultivate very deeply, usually by digging parallel contiguous trenches in succession, filling each from the next; as, to trench a garden for certain crops. [1913 Webster]

trench, v. i.

To encroach; to intrench. [1913 Webster]
"Does it not seem as if for a creature to challenge to itself a boundless attribute, were to trench upon the prerogative of the divine nature?" [1913 Webster]
To have direction; to aim or tend. Bacon. [1913 Webster]
"Like powerful armies, trenching at a town
By slow and silent, but resistless, sap." [1913 Webster]

To trench at, to make trenches against; to approach by trenches, as a town in besieging it. [Obs.]

trench, n. [OE. trenche, F. tranchée. See Trench, v. t.].

A long, narrow cut in the earth; a ditch; as, a trench for draining land. Mortimer. [1913 Webster]
An alley; a narrow path or walk cut through woods, shrubbery, or the like. [1913 Webster]
"In a trench, forth in the park, goeth she." [1913 Webster]
An excavation made during a siege, for the purpose of covering the troops as they advance toward the besieged place. The term includes the parallels and the approaches. [1913 Webster]

To open the trenches (Mil.), to begin to dig or to form the lines of approach. -- Trench cavalier (Fort.), an elevation constructed (by a besieger) of gabions, fascines, earth, and the like, about half way up the glacis, in order to discover and enfilade the covered way. -- Trench plow, or Trench plough, a kind of plow for opening land to a greater depth than that of common furrows.

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OXFORD DICTIONARY

trench, n. & v.
--n.
1 a long narrow usu. deep depression or ditch.
2 Mil. a this dug by troops to stand in and be sheltered from enemy fire. b (in pl.) a defensive system of these.
3 a long narrow deep depression in the ocean bed.
--v.
1 tr. dig a trench or trenches in (the ground).
2 tr. turn over the earth of (a field, garden, etc.) by digging a succession of adjoining ditches.
3 intr. (foll. by on, upon) archaic a encroach. b verge or border closely.

Idiom

trench coat
1 a soldier's lined or padded waterproof coat.
2 a loose belted raincoat. trench fever a highly infectious disease transmitted by lice, that infested soldiers in the trenches in the war of 1914-18. trench mortar a light simple mortar throwing a bomb from one's own into the enemy trenches. trench warfare hostilities carried on from more or less permanent trenches.

Etymology

ME f. OF trenche (n.) trenchier (v.), ult. f. L truncare TRUNCATE

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THESAURUS

trench

Bassalia, abri, abysm, abyss, abyssal zone, adit, air-raid shelter, approach, approach trench, aqueduct, arroyo, barge in, bathyal zone, benthos, bomb shelter, bombproof, bore, bottom, bottom glade, bottom waters, bottomless depths, bottoms, box canyon, breach, break, break in, break in upon, bunker, burrow, burst in, butt in, canal, canalization, canalize, canyon, carve, cave, cavity, chamfer, channel, channelize, chap, charge in, chasm, check, chimney, chink, chisel, cleave, cleft, cleuch, clough, col, concealment, conduct, conduit, convey, corrugate, coulee, couloir, countermine, coupure, course, cover, covert, coverture, crack, cranny, crash, crash in, crash the gates, creep in, crevasse, crevice, crimp, crowd in, cut, cut apart, cut in, cwm, cyclone cellar, dado, dale, defile, dell, delve, dig, dig out, dike, dingle, ditch, donga, double sap, drain, draw, dredge, drill, drive, duct, dugout, earth, edge in, egress, elbow in, encroach, engrave, entrance, entrench, entrenchment, excavate, excavation, exit, fallout shelter, fault, fire trench, fissure, flaw, flume, flute, flying sap, foist in, fortified tunnel, fosse, foxhole, fracture, funk hole, funnel, furrow, gallery, gap, gape, gash, gill, glen, goffer, gorge, gouge, gouge out, groove, ground, grove, grub, gulch, gulf, gully, gutter, ha-ha, hole, horn in, impinge, impose, impose on, impose upon, incise, incision, infiltrate, infringe, ingress, inner space, insinuate, interfere, interlope, interpose, intervale, intervene, intrude, invade, irrupt, joint, kennel, kloof, leak, lower, lunar rill, mine, moat, notch, nullah, obtrude, ocean bottom, ocean depths, ocean floor, open, opening, parallel, pass, passage, passageway, pelagic zone, pipe, pleat, plow, press in, push in, put on, put through, put upon, quarry, rabbet, ravine, rent, rifle, rift, rime, rive, rupture, rush in, rut, safety zone, sap, scissure, scoop, scoop out, score, scrabble, scrape, scratch, seam, shelter, shovel, sink, siphon, slink in, slip in, slit, slit trench, slot, smash in, sneak in, spade, split, squeeze in, steal in, storm cave, storm cellar, storm in, strath, streak, striate, sunk fence, the deep, the deep sea, the deeps, the depths, throng in, thrust in, trespass, trough, troughing, troughway, tunnel, vale, valley, verge, void, wadi, way, work in, worm in, wrinkle

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ROGET THESAURUS

trench

Defense

N defense, protection, guard, ward, shielding, propugnation, preservation, guardianship, area defense, site defense, self-defense, self-preservation, resistance, safeguard, balistraria, bunker, screen, camouflage, fortification, munition, muniment, trench, foxhole, bulwark, fosse, moat, ditch, entrenchment, intrenchment, kila, dike, dyke, parapet, sunk fence, embankment, mound, mole, bank, sandbag, revetment, earth work, field- work, fence, wall dead wall, contravallation, paling, palisade, haha, stockade, stoccado, laager, sangar, barrier, barricade, boom, portcullis, chevaux de frise, abatis, abattis, abbatis, vallum, circumvallation, battlement, rampart, scarp, escarp, counter-scarp, glacis, casemate, vallation, vanfos, buttress, abutment, shore, breastwork, banquette, curtain, mantlet, bastion, redan, ravelin, vauntmure, advance work, horn work, outwork, barbacan, barbican, redoubt, fort-elage, fort-alice, lines, loophole, machicolation, sally port, hold, stronghold, fastness, asylum, keep, donjon, dungeon, fortress, citadel, capitol, castle, tower of strength, tower of strength, fort, barracoon, pah, sconce, martello tower, peelhouse, blockhouse, rath, wooden walls, bulletproof vest, armored vest, buffer, corner stone, fender, apron, mask, gauntlet, thimble, carapace, armor, shield, buckler, aegis, breastplate, backplate, cowcatcher, face guard, scutum, cuirass, habergeon, mail, coat of mail, brigandine, hauberk, lorication, helmet, helm, bassinet, salade, heaume, morion, murrion, armet, cabaset, vizor, casquetel, siege cap, headpiece, casque, pickelhaube, vambrace, shako, bearskin, panoply, truncheon, garrison, picket, piquet, defender, protector, guardian, bodyguard, champion, knight-errant, Paladin, propugner, bulletproof window, hardened site, defending, defensive, mural, armed, armed at all points, armed cap-a-pie, armed to the teeth, panoplied, iron-plated, ironclad, loopholed, castellated, machicolated, casemated, defended, proof against, armored, ballproof, bulletproof, hardened, defensively, on the defense, on the defensive, in defense, at bay, pro aris et focis, Int, no surrender!, defense not defiance, Dieu defend le droit, fidei defensor, defender of the faith.

Furrow

N furrow, groove, rut, sulcus, scratch, streak, striae, crack, score, incision, slit, chamfer, fluting, corduroy road, cradle hole, channel, gutter, trench, ditch, dike, dyke, moat, fosse, trough, kennel, ravine, tajo, thank-ye-ma'am, furrowed, ribbed, striated, sulcated, fluted, canaliculated, bisulcous, bisulcate, bisulcated, canaliferous, trisulcate, corduroy, unisulcate, costate, rimiform.

Insulation

N insulation, fire extinction, insulation, incombustible material, noncombustible material, fire retardant, flame retardant, fire wall, fire door, incombustibility, incombustibleness, extincteur, fire annihilator, amianth, amianthus, earth-flax, mountain-flax, asbestos, fireman, fire fighter, fire eater, fire department, fire brigade, engine company, pumper, fire truck, hook and ladder, aerial ladder, bucket, fire hose, fire hydrant, backfire, firebreak, trench, aerial water bombardment, wet blanket, fire extinguisher, soda and acid extinguisher, dry chemical extinguisher, CO-two extinguisher, carbon tetrachloride, foam, sprinklers, automatic sprinkler system, fire bucket, sand bucket, fire alarm, evacuation alarm, fire code, fire regulations, fire, fire inspector, code violation, citation, incombustible, nonflammable, uninflammable, unflammable, fireproof, fight fire with fire.

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