The Collaborative International Dictionary of English v.0.48:

Plenty \Plen"ty\, a.
   Plentiful; abundant. [Obs. or Colloq.]
   [1913 Webster]

         If reasons were as plenty as blackberries. --Shak.
                                                  (Folio ed.)
   [1913 Webster]

         Those countries where shrubs are plenty. --Goldsmith.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plenty \Plen"ty\, n.; pl. Plenties, in --Shak. [OE. plentee,
   plente, OF. plent['e], fr. L. plenitas, fr. plenus full. See
   Full, a., and cf. Complete.]
   Full or adequate supply; enough and to spare; sufficiency;
   specifically, abundant productiveness of the earth; ample
   supply for human wants; abundance; copiousness. "Plenty of
   corn and wine." --Gen. xxvii. 28. "Promises Britain peace and
   plenty." --Shak.
   [1913 Webster]

         Houses of office stuffed with plentee.   --Chaucer.
   [1913 Webster]

         The teeming clouds Descend in gladsome plenty o'er the
         world.                                   --Thomson.
   [1913 Webster]

   Syn: Abundance; exuberance. See Abundance.
        [1913 Webster]

WordNet (r) 3.0 (2006):

plenty
    adv 1: as much as necessary; "Have I eaten enough?"; (`plenty'
           is nonstandard) "I've had plenty, thanks" [syn: enough,
           plenty]
    n 1: a full supply; "there was plenty of food for everyone"
         [syn: plenty, plentifulness, plenteousness,
         plenitude, plentitude]
    2: (often followed by `of') a large number or amount or extent;
       "a batch of letters"; "a deal of trouble"; "a lot of money";
       "he made a mint on the stock market"; "see the rest of the
       winners in our huge passel of photos"; "it must have cost
       plenty"; "a slew of journalists"; "a wad of money" [syn:
       batch, deal, flock, good deal, great deal,
       hatful, heap, lot, mass, mess, mickle, mint,
       mountain, muckle, passel, peck, pile, plenty,
       pot, quite a little, raft, sight, slew, spate,
       stack, tidy sum, wad]

Moby Thesaurus II by Grady Ward, 1.0:

272 Moby Thesaurus words for "plenty":
   a deal, a great deal, a lot, abounding, abundance, abundant,
   abundantly, accumulation, acres, adequate, affluence, affluent,
   all-sufficing, amassment, ample, ample sufficiency, ampleness,
   amplitude, aplenty, as all creation, as all get-out, avalanche,
   backlog, bags, barely sufficient, barrels, beaucoup, bonanza,
   bottomless, bounteous, bountiful, bountifulness, bountiousness,
   budget, bumper crop, bushel, collection, commensurate,
   commissariat, commissary, competent, considerable, considerably,
   copious, copiousness, cornucopia, corresponding, countlessness,
   cumulation, decent, deluge, diffuse, due, dump, effuse,
   embarras de richesses, enough, epidemic, equal to, ever so,
   ever so much, exhaustless, extravagance, extravagancy, extravagant,
   exuberance, exuberant, fat, fertile, fertility, fit, flood, flow,
   flush, foison, full, full measure, fullness, galore, generosity,
   generous, generousness, good, good enough, great abundance,
   great deal, great plenty, greatly, gush, heap, heaps, highly,
   hoard, in great measure, in plenty, in quantity, inexhaustible,
   infinitude, innumerability, inundation, inventory, landslide,
   larder, largely, lavish, lavishness, liberal, liberality,
   liberalness, load, loads, lot, lots, luxuriance, luxuriant, many,
   manyness, mass, masses, material, materials, materiel, maximal,
   maximum, mess, minimal, minimum, money to burn, more than enough,
   mountain, mountains, much, muchly, multifariousness, multifoldness,
   multiplicity, multitude, multitudes, multitudinousness, munitions,
   myriad, myriads, never so, no end, no end of, not a little,
   numbers, numerous, numerousness, ocean, oceans, oodles, opulence,
   opulency, opulent, outpouring, overabundance, overaccumulation,
   overbounteousness, overcopiousness, overdose, overflow,
   overflowing, overlavishness, overluxuriance, overmeasure,
   overmuchness, overnumerousness, overplentifulness, overplenty,
   overpopulation, overprofusion, oversufficiency, oversupply, pack,
   peck, pile, piles, plenitude, plenitudinous, plenteous,
   plenteousness, plentiful, plentifulness, plenty good enough,
   plethora, pretty much, prevailing, prevalence, prevalent, prodigal,
   prodigality, productive, productiveness, profuse, profuseness,
   profusion, profusive, proportionate, provisionment, provisions,
   quantities, quantity, rampant, rations, redundancy, repertoire,
   repertory, replete, repleteness, repletion, rich, rich harvest,
   rich vein, richness, rick, rife, rifeness, riot, riotous,
   riotousness, running over, satisfactory, scads, scores, sea,
   shower, sight, slews, so, so very much, spate, stack, stacks,
   stock, stock-in-trade, stockpile, store, stores, stream,
   substantial, substantiality, substantialness, sufficient,
   sufficient for, sufficing, suitable, superabundance, superabundant,
   superfluity, superflux, supplies, supply on hand, swarmingness,
   teeming, teemingness, to the skies, tons, treasure, treasury,
   up to, very much, volume, wealth, wealthy, well-found,
   well-furnished, well-provided, well-stocked, wholesale, world,
   worlds