The Collaborative International Dictionary of English v.0.48:

Prodigal \Prod"i*gal\, a. [L. prodigus, from prodigere to drive
   forth, to squander away; pro forward, forth + agere to drive;
   cf. F. prodigue. See Agent. ]
   Given to extravagant expenditure; expending money or other
   things without necessity; recklessly or viciously profuse;
   lavish; wasteful; not frugal or economical; as, a prodigal
   man; the prodigal son; prodigal giving; prodigal expenses.
   [1913 Webster]

         In fighting fields [patriots] were prodigal of blood.
                                                  --Dryden.
   [1913 Webster]

   Syn: Profuse; lavish; extravagant; squandering; wasteful. See
        Profuse.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Prodigal \Prod"i*gal\, n.
   One who expends money extravagantly, viciously, or without
   necessity; one that is profuse or lavish in any expenditure;
   a waster; a spendthrift. "Noble prodigals of life." --Trench.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prodigal
    adj 1: recklessly wasteful; "prodigal in their expenditures"
           [syn: extravagant, prodigal, profligate,
           spendthrift]
    n 1: a recklessly extravagant consumer [syn: prodigal,
         profligate, squanderer]

Moby Thesaurus II by Grady Ward, 1.0:

208 Moby Thesaurus words for "prodigal":
   Adamic, abounding, abundant, affluent, aggrandized, alive with,
   all-sufficing, ample, amplified, aplenty, backsliding, ballyhooed,
   bibulous, big-time spender, bottomless, bounteous, bountiful,
   bristling, bursting, carnal, copious, crapulent, crapulous,
   crawling, crowded, crowding, diffuse, diffusive, disproportionate,
   dissipative, easy come, easy go, effuse, effusive, epidemic,
   erring, exaggerated, excessive, exhaustless, exorbitant,
   extravagant, extreme, exuberant, fallen, fat, fecund, fertile,
   fleshly, flush, formless, frail, full, galore, generous,
   gluttonous, grandiloquent, gushing, gushy, high-flown, hyperbolic,
   immoderate, improvident, impure, in plenty, in profusion,
   in quantity, incontinent, indulgent, inexhaustible, infirm,
   inflated, inordinate, intemperate, jam-packed, jammed, lapsed,
   lavish, liberal, lush, luxuriant, magnified, many, maximal, much,
   numerous, of easy virtue, opulent, overabundant, overbounteous,
   overcopious, overdone, overdrawn, overemphasized, overemphatic,
   overestimated, overexuberant, overflowing, overgenerous, overgreat,
   overindulgent, overindulging, overlarge, overlavish, overliberal,
   overluxuriant, overmuch, overnumerous, overplenteous,
   overplentiful, overplenty, overpopulated, overpopulous,
   overpraised, overprolific, oversold, overstated, overstressed,
   overwrought, packed, peccable, penny-wise and pound-foolish,
   plenitudinous, plenteous, plentiful, plenty, pleonastic, plethoric,
   populous, postlapsarian, pound-foolish, prevailing, prevalent,
   prodigal son, productive, profligate, profuse, profusive,
   proliferating, prolific, puffed, pullulating, rampant, recidivist,
   recidivistic, reckless, redundant, reiterative, repetitive,
   replete, rich, rife, riotous, running over, self-indulgent,
   spend-all, spender, spendthrift, squanderer, squandering,
   stretched, studded, sumptuous, superabundant, superlative,
   swarming, swinish, tautologous, teeming, thick, thick as hail,
   thick with, thick-coming, thriving, thronged, thronging, too much,
   touted, unangelic, unbridled, unchaste, unclean, unconstrained,
   uncontrolled, undisciplined, unfrugal, ungodly, ungood, unlimited,
   unmeasured, unrestrained, unrighteous, unsaintly, unthrifty,
   unvirtuous, virtueless, wanton, wasteful, waster, wastethrift,
   wastrel, wayward, weak, wealthy, well-found, well-furnished,
   well-provided, well-stocked, wholesale



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

PRODIGAL, civil law, persons. Prodigals were persons who, though of full
age, were incapable of managing their affairs, and of the obligations which
attended them, in consequence of their bad conduct, and for whom a curator
was therefore appointed.
     2. In Pennsylvania, by act of assembly, an habitual drunkard is
deprived of the management of his affairs, when he wastes his property, and
his estate is placed in the bands of a committee.