The Collaborative International Dictionary of English v.0.48:

Impoverish \Im*pov"er*ish\, v. t. [imp. & p. p. Impoverished;
   p. pr. & vb. n. Impoverishing.] [OF. empovrir; pref. em-
   (L. in) + povre poor, F. pauvre; cf. OF. apovrir, F.
   appauvrir, where the prefix is a-, L. ad. Cf. Empoverish,
   and see Poor, and -ish.]
   1. To make poor; to reduce to poverty or indigence; as,
      misfortune and disease impoverish families.
      [1913 Webster]

   2. To exhaust the strength, richness, or fertility of; to
      make sterile; as, to impoverish land.
      [1913 Webster]

WordNet (r) 3.0 (2006):

impoverished
    adj 1: poor enough to need help from others [syn: destitute,
           impoverished, indigent, necessitous, needy,
           poverty-stricken]
    2: destroyed financially; "the broken fortunes of the family"
       [syn: broken, wiped out(p), impoverished]