The Collaborative International Dictionary of English v.0.48:

Spendthrift \Spend"thrift\, a.
   Prodigal; extravagant; wasteful.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spendthrift \Spend"thrift`\, n.
   One who spends money profusely or improvidently; a prodigal;
   one who lavishes or wastes his estate. Also used
   figuratively.
   [1913 Webster]

         A woman who was a generous spendthrift of life. --Mrs.
                                                  R. H. Davis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spendthrift
    adj 1: recklessly wasteful; "prodigal in their expenditures"
           [syn: extravagant, prodigal, profligate,
           spendthrift]
    n 1: someone who spends money prodigally [syn: spendthrift,
         spend-all, spender, scattergood]