The Collaborative International Dictionary of English v.0.48:

Ditch \Ditch\, v. t. [imp. & p. p. Ditched; p. pr. & vb. n.
   Ditching.]
   1. To dig a ditch or ditches in; to drain by a ditch or
      ditches; as, to ditch moist land.
      [1913 Webster]

   2. To surround with a ditch. --Shak.
      [1913 Webster]

   3. To throw into a ditch; as, the engine was ditched and
      turned on its side.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ditch \Ditch\, v. i.
   To dig a ditch or ditches. --Swift.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ditch \Ditch\ (?; 224), n.; pl. Ditches. [OE. dich, orig. the
   same word as dik. See Dike.]
   1. A trench made in the earth by digging, particularly a
      trench for draining wet land, for guarding or fencing
      inclosures, or for preventing an approach to a town or
      fortress. In the latter sense, it is called also a moat
      or a fosse.
      [1913 Webster]

   2. Any long, narrow receptacle for water on the surface of
      the earth.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ditch
    n 1: a long narrow excavation in the earth
    2: any small natural waterway
    v 1: forsake; "ditch a lover"
    2: throw away; "Chuck these old notes" [syn: chuck, ditch]
    3: sever all ties with, usually unceremoniously or
       irresponsibly; "The company dumped him after many years of
       service"; "She dumped her boyfriend when she fell in love
       with a rich man" [syn: dump, ditch]
    4: make an emergency landing on water
    5: crash or crash-land; "ditch a car"; "ditch a plane"
    6: cut a trench in, as for drainage; "ditch the land to drain
       it"; "trench the fields" [syn: trench, ditch]

Moby Thesaurus II by Grady Ward, 1.0:

252 Moby Thesaurus words for "ditch":
   abandon, abri, abysm, abyss, adit, alight, approach trench,
   aqueduct, arch dam, arroyo, backstop, bamboo curtain, bank, bar,
   barrage, barrier, bear-trap dam, beaver dam, beg, boom, box canyon,
   breach, break, breakwater, breastwork, brick wall, buffer,
   bulkhead, bulwark, bunker, bury, cache, canal, canalization,
   canalize, canyon, carve, cashier, cast, cast aside, cast away,
   cast off, cavity, chamfer, channel, chap, chasm, check, chimney,
   chink, chisel, chuck, circumvent, cleave, cleft, cleuch, clough,
   cofferdam, col, come down, come in, communication trench, conceal,
   conduit, corrugate, coulee, couloir, countermine, coupure, course,
   cover, crack, cranny, crash-land, crevasse, crevice, crimp, cut,
   cut apart, cwm, dado, dam, deep-six, defense, defile, dell,
   descend, dike, discard, dispose of, ditch, donga, double,
   double sap, downwind, draw, duct, dugout, dump, earthwork, egress,
   eighty-six, eliminate, elude, embankment, engrave, ensconce,
   entrance, entrenchment, escape, evade, excavation, exit, fault,
   fence, fire trench, fissure, flaw, flume, flute, flying sap,
   fortified tunnel, fosse, foxhole, fracture, furrow, gallery, gap,
   gape, gash, gate, get around, get away from, get out of,
   get quit of, get rid of, get shut of, give away, goffer, gorge,
   gouge, gravity dam, groin, groove, gulch, gulf, gully, gutter,
   ha-ha, hide, hole, hydraulic-fill dam, incise, incision, ingress,
   iron curtain, jam, jettison, jetty, jilt, joint, junk, kennel,
   kloof, land, leak, leaping weir, levee, level off, light, logjam,
   milldam, mine, moat, mole, mound, notch, nullah, occult, open,
   opening, overshoot, pancake, parallel, parapet, part with, pass,
   passage, passageway, pleat, plow, portcullis, rabbet, rampart,
   ravine, reject, remove, rent, rifle, rift, rime, rive, roadblock,
   rock-fill dam, rupture, rut, sap, scissure, score, scrap, scratch,
   screen, seam, seawall, secrete, settle down, shake, shake off,
   shuffle out of, shutter dam, skirt, slit, slit trench, slot,
   slough, split, stone wall, streak, striate, sunk fence, talk down,
   throw away, throw out, throw over, throw overboard, toss overboard,
   touch down, trench, trough, troughing, troughway, tunnel, upwind,
   valley, void, wadi, wall, way, weir, wicket dam, work, wrinkle