The Collaborative International Dictionary of English v.0.48:

Sloppy \Slop"py\, a. [Compar. Sloppier; superl. Sloppiest.]
   [From Slop.]
   Wet, so as to spatter easily; wet, as with something slopped
   over; muddy; plashy; as, a sloppy place, walk, road.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sloppy
    adj 1: lacking neatness or order; "a sloppy room"; "sloppy
           habits"
    2: wet or smeared with a spilled liquid or moist material; "a
       sloppy floor"; "a sloppy saucer"
    3: (of soil) soft and watery; "the ground was boggy under foot";
       "a marshy coastline"; "miry roads"; "wet mucky lowland";
       "muddy barnyard"; "quaggy terrain"; "the sloughy edge of the
       pond"; "swampy bayous" [syn: boggy, marshy, miry,
       mucky, muddy, quaggy, sloppy, sloughy, soggy,
       squashy, swampy, waterlogged]
    4: not fitting closely; hanging loosely; "baggy trousers"; "a
       loose-fitting blouse is comfortable in hot weather" [syn:
       baggy, loose-fitting, sloppy]
    5: excessively or abnormally emotional [syn: overemotional,
       sloppy]
    6: marked by great carelessness; "a most haphazard system of
       record keeping"; "slapdash work"; "slipshod spelling";
       "sloppy workmanship" [syn: haphazard, slapdash,
       slipshod, sloppy]

Moby Thesaurus II by Grady Ward, 1.0:

219 Moby Thesaurus words for "sloppy":
   all thumbs, amateurish, aquatic, aqueous, awkward, bagging, baggy,
   barfy, bathetic, beat-up, bedraggled, beery, blowzy, blunderheaded,
   blundering, boorish, boozy, botched, bumbling, bungling,
   butterfingered, canned, careless, chintzy, clownish, cloying,
   clumsy, clumsy-fisted, dangling, deficient, dilapidated, dirty,
   disguised, disgusting, disheveled, disordered, disorderly, dowdy,
   drabbletailed, draggled, draggletailed, drooping, drunk, easy,
   easygoing, fecal, feculent, fetid, filthy, fingers all thumbs,
   flapping, flyblown, foul, frowzy, frumpish, frumpy, fumbling,
   gauche, gawkish, gawky, gloppy, gooey, graceless, grubby, grungy,
   gunky, gushing, gushy, half-assed, ham-fisted, ham-handed, hanging,
   haphazard, heavy-handed, hit-and-miss, hit-or-miss, hulking, hulky,
   hydrated, hydraulic, hydrous, icky, impotent, imprecise, in rags,
   indifferent, inebriated, inelegant, informal, lax, left-hand,
   left-handed, lenient, liquid, loose, loutish, lubberly, lumbering,
   lumpen, lumpish, maggoty, maladroit, malodorous, maudlin, mawkish,
   mediocre, mephitic, messy, miry, mucky, muddled, muddy, mushy,
   mussy, namby-pamby, nasty, nauseating, negligent, nostalgic,
   nostomanic, oafish, odious, oozy, ordurous, overindulgent,
   overpermissive, oversentimental, oversentimentalized, permissive,
   pixilated, plashy, plastered, poky, ponderous, poor, promiscuous,
   puky, putrid, ragged, raggedy, rainy, rank, relaxed, remiss,
   repulsive, rickety, romantic, rotten, ruinous, sappy, scabby,
   scraggly, scruffy, scummy, scurfy, seedy, sentimental,
   sentimentalized, shabby, shaky, shitty, shoddy, slabby, slack,
   slapdash, slatternly, slimy, slipshod, slipshoddy, slobbering,
   slobbery, slobby, sloshy, sloughy, slovenly, sludgy, slushy,
   sluttish, sodden, soft, soggy, sopping, soppy, sordid, splashy,
   sposhy, squalid, squashy, squelchy, squishy, sticky, stiff,
   streaming, swashy, tacky, tattered, tear-jerking, teary, turbid,
   uncouth, unfastidious, ungainly, ungraceful, unhandy, unkempt,
   unneat, unrestrained, unsightly, unthorough, untidy, unwieldy,
   vile, vomity, waterish, watery, weak, wet, wormy, yecchy