The Collaborative International Dictionary of English v.0.48:

Turf \Turf\ (t[^u]rf), n.; pl. Turfs (t[^u]rfs), Obs. Turves
   (t[^u]rvz). [AS. turf; akin to D. turf peat, G. torf, OHG.
   zurba turf, Sw. & Icel. torf turf, peat, Dan. t["o]rv, Skr.
   darbha a kind of grass, a tuft of grass. [root]242.]
   1. That upper stratum of earth and vegetable mold which is
      filled with the roots of grass and other small plants, so
      as to adhere and form a kind of mat; sward; sod.
      [1913 Webster]

            At his head a grass-green turf.       --Shak.
      [1913 Webster]

            The Greek historian sets her in the field on a high
            heap of turves.                       --Milton.
      [1913 Webster]

   2. Peat, especially when prepared for fuel. See Peat.
      [1913 Webster]

   3. Race course; horse racing; -- preceded by the. "We . . .
      claim the honors of the turf." --Cowper.
      [1913 Webster]

   Note: Turf is often used adjectively, or to form compounds
         which are generally self-explaining; as, turf ashes,
         turf cutter or turf-cutter, turf pit or turf-pit,
         turf-built, turf-clad, turf-covered, etc.
         [1913 Webster]

   Turf ant (Zool.), a small European ant (Formica flava)
      which makes small ant-hills on heaths and commons.

   Turf drain, a drain made with turf or peat.

   Turf hedge, a hedge or fence formed with turf and plants of
      different kinds.

   Turf house, a house or shed formed of turf, common in the
      northern parts of Europe.

   Turf moss a tract of turfy, mossy, or boggy land.

   Turf spade, a spade for cutting and digging turf, longer
      and narrower than the common spade.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Turf \Turf\, v. t. [imp. & p. p. Turfed; p. pr. & vb. n.
   Turfing.]
   To cover with turf or sod; as, to turf a bank, or the border
   of a terrace. --A. Tucker.
   [1913 Webster]

WordNet (r) 3.0 (2006):

turf
    n 1: surface layer of ground containing a mat of grass and grass
         roots [syn: turf, sod, sward, greensward]
    2: the territory claimed by a juvenile gang as its own
    3: range of jurisdiction or influence; "a bureaucracy...chiefly
       concerned with turf...and protecting the retirement system"
    v 1: cover (the ground) with a surface layer of grass or grass
         roots

Moby Thesaurus II by Grady Ward, 1.0:

117 Moby Thesaurus words for "turf":
   alcohol, ambit, archery ground, area, athletic field, backyard,
   badminton court, bailiwick, banish, baseball field,
   basketball court, benzine, billiard parlor, bounce, bowling alley,
   bowling green, briquette, burnable, butane, carbon, charcoal, coal,
   coke, combustible, constituency, course, court, cricket ground,
   croquet ground, croquet lawn, diamond, dismiss, divot, dope, eject,
   ethane, ethanol, exile, expel, fairway, field, fire, fireball,
   firing, flammable, flammable material, football field, footing,
   fuel, fuel additive, fuel dope, gas, gas carbon, gasoline,
   glaciarium, golf course, golf links, grass, green, greensward,
   gridiron, gym, gymnasium, heptane, hexane, ice rink, infield,
   inflammable, inflammable material, isooctane, jet fuel, kerosene,
   lawn, links, methane, methanol, natural gas, octane, oil, orbit,
   oust, outfield, oval, paraffin, peat, pentane, playground,
   playing field, playroom, polo ground, pool hall, poolroom, propane,
   propellant, putting green, racecourse, racing, racket court,
   region, rink, rocket fuel, sack, skating rink, soccer field, sod,
   sphere, sphere of influence, squash court, stamping ground,
   stretch, sward, tennis court, territory, the turf, throw out,
   track, vantage