The Collaborative International Dictionary of English v.0.48:

Slut \Slut\ (sl[u^]t), n. [OE. slutte; cf. OD. slodde a slut,
   Icel. sl["o]ttr a heavy, loglike fellow, slota to droop.]
   1. An untidy woman; a slattern.
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            Sluts are good enough to make a sloven's porridge.
                                                  --Old Proverb.
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   2. A servant girl; a drudge. [Obs.]
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            Our little girl Susan is a most admirable slut, and
            pleases us mightily, doing more service than both
            the others.                           --Pepys.
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   3. A female dog; a bitch.
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WordNet (r) 3.0 (2006):

slut
    n 1: a dirty untidy woman [syn: slattern, slut, slovenly
         woman, trollop]
    2: a woman adulterer [syn: adulteress, fornicatress,
       hussy, jade, loose woman, slut, strumpet,
       trollop]