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]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "spendthrift":
   big-time spender, dissipative, easy come, easy go, extravagant,
   improvident, incontinent, intemperate, lavish, overgenerous,
   overlavish, overliberal, penny-wise and pound-foolish,
   pound-foolish, prodigal, prodigal son, profligate, profuse,
   spend-all, spender, squanderer, squandering, wasteful, waster,
   wastethrift, wastrel



Bouvier's Law Dictionary, Revised 6th Ed (1856):

SPENDTHRIFT. By the Rev. Stat. of Vermont, tit. 16, c. 65, s. 9, spendthrift
is defined to be a person who by excessive drinking) gaming, idleness or
debauchery of any kind, shall so spend, waste, or lessen his estate as to
expose himself or his family to want or suffering, or expose the town to
charge or expense, for support of himself or family.