The Collaborative International Dictionary of English v.0.48:

Slatternly \Slat"tern*ly\, a.
   Resembling a slattern; sluttish; negligent; dirty. -- adv. In
   a slatternly manner.
   [1913 Webster]

WordNet (r) 3.0 (2006):

slatternly
    adj 1: characteristic of or befitting a slut or slattern; used
           especially of women [syn: blowsy, blowzy,
           slatternly, sluttish]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "slatternly":
   beat-up, bedraggled, blowsy, blowzy, careless, chintzy,
   dilapidated, dirty, disheveled, disordered, dowdy, drabbletailed,
   draggled, draggletailed, filthy, foul, frowsy, frowzy, frumpish,
   frumpy, grimy, grubby, in rags, informal, loose, lumpen, messy,
   mussy, neglected, negligent, poky, ragged, raggedy, ruinous,
   scraggly, seedy, shabby, shoddy, slack, slattern, slipshod, sloppy,
   slovenly, sluttish, sordid, squalid, tacky, tattered, unkempt,
   unneat, unsightly, untidy