The Collaborative International Dictionary of English v.0.48:

Spate \Spate\, n. [Of Celtic origin; cf. Ir. speid.]
   A river flood; an overflow or inundation. --Burns.
   [1913 Webster]

         Gareth in a showerful spring
         Stared at the spate.                     --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spate
    n 1: (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]
    2: a sudden forceful flow [syn: rush, spate, surge,
       upsurge]
    3: the occurrence of a water flow resulting from sudden rain or
       melting snow [syn: freshet, spate]

Moby Thesaurus II by Grady Ward, 1.0:

258 Moby Thesaurus words for "spate":
   Niagara, abundance, acres, affluence, afflux, affluxion,
   ample sufficiency, ampleness, amplitude, army, asperse, avalanche,
   bags, barrels, batch, befoul, belch, bespatter, bespot, blacken,
   bonanza, bountifulness, bountiousness, brash, bumper crop, burst,
   burst of rain, bushel, cascade, cataclysm, cataract, cloudburst,
   cluster, cohue, concourse, confluence, conflux, considerable,
   copiousness, countlessness, course, crosscurrent, crowd, crush,
   current, deal, debouchment, defame, defluxion, deluge, denigrate,
   dissiliency, douse, downfall, downflow, downpour, drencher, drift,
   driftage, embarras de richesses, enough, eructation, eruption,
   extravagance, extravagancy, exuberance, fertility, flare-up, flock,
   flood, flooding, flow, flowing, fluency, flux, foison, fresh,
   freshet, full measure, fullness, galaxy, generosity, generousness,
   gobs, good deal, great abundance, great deal, great plenty, gush,
   gushing rain, heap, heaps, heavy rain, horde, host, inflow,
   inundation, jam, jet, landslide, lashings, lavishness, legion,
   liberality, liberalness, load, loads, lot, lots, luxuriance, mass,
   maximum, mess, mill run, millrace, mint, mob, money to burn,
   more than enough, mountain, much, multitude, myriad, myriads,
   numerousness, ocean, oceans, onrush, onset, onward course, oodles,
   opulence, opulency, outbreak, outburst, outflow, outflowing,
   outpouring, overabundance, overaccumulation, overbounteousness,
   overcopiousness, overdose, overflow, overlavishness,
   overluxuriance, overmeasure, overmuchness, overnumerousness,
   overplentifulness, overplenty, overpopulation, overprofusion,
   oversufficiency, oversupply, pack, panoply, peck, pile, piles,
   plash, plenitude, plenteousness, plentifulness, plenty, plethora,
   pot, pour, press, prevalence, prodigality, productiveness,
   profuseness, profusion, progression, quantities, quantity,
   quite a little, rabble, race, raft, rafts, rain, rainburst,
   rainspout, rainstorm, rapids, redundancy, repleteness, repletion,
   rich harvest, rich vein, richness, riot, riotousness, river, rout,
   ruck, run, rush, scads, scud, sea, series, set, shower, sight,
   slew, slews, slop, slosh, slur, smear, soaker, soaking rain,
   sparge, spew, spit, splatter, splosh, splurge, splutter, spout,
   spurt, spurtle, stack, stacks, stream, substantiality,
   substantialness, succession, superabundance, superfluity,
   superflux, surge, swash, teemingness, throng, tide, tidy sum, tons,
   torrent, torrent of rain, traduce, trend, undercurrent, undertow,
   volcan, volume, wad, wads, water flow, waterflood, waterspout,
   wealth, whole slew, world, worlds