The Collaborative International Dictionary of English v.0.48:

Slum \Slum\ (sl[u^]m), n. [CF. Slump, n.]
   1. A foul back street of a city, especially one filled with a
      poor, dirty, degraded, and often vicious population; any
      low neighborhood or dark retreat; -- usually in the
      plural; as, Westminster slums are haunts for theives.
      --Dickens.
      [1913 Webster]

   2. pl. (Mining) Same as Slimes.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slum \Slum\ (sl[u^]m), v. i.
   To visit or frequent slums, esp. out of curiosity, or for
   purposes of study, etc. Also called go slumming. [Colloq.]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

slum
    n 1: a district of a city marked by poverty and inferior living
         conditions [syn: slum, slum area]
    v 1: spend time at a lower socio-economic level than one's own,
         motivated by curiosity or desire for adventure; usage
         considered condescending and insensitive; "attending a
         motion picture show by the upper class was considered
         sluming in the early 20th century"