The Collaborative International Dictionary of English v.0.48:

Plenitude \Plen"i*tude\, n. [L. plenitudo, fr. plenus full; cf.
   F. plenitude.]
   1. The quality or state of being full or complete; fullness;
      completeness; abundance; as, the plenitude of space or
      power.
      [1913 Webster]

   2. Animal fullness; repletion; plethora. [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

plenitude
    n 1: a full supply; "there was plenty of food for everyone"
         [syn: plenty, plentifulness, plenteousness,
         plenitude, plentitude]

Moby Thesaurus II by Grady Ward, 1.0:

191 Moby Thesaurus words for "plenitude":
   abundance, accumulation, acres, affluence, amassment,
   ample sufficiency, ampleness, amplitude, avalanche, backlog, bags,
   barrels, bonanza, boundlessness, bountifulness, bountiousness,
   budget, bulk, bumper crop, bushel, ceaselessness, collection,
   commissariat, commissary, completeness, congestion,
   consecutiveness, constancy, constant flow, continualness,
   continuity, continuousness, copiousness, cornucopia, countlessness,
   cumulation, dump, endlessness, enormity, enormousness, entireness,
   equilibrium, expanse, extravagance, exuberance, featurelessness,
   fertility, flood, flood tide, flow, foison, formidableness, full,
   full measure, fullness, gaplessness, generosity, generousness,
   gigantism, grandeur, grandness, great abundance, great plenty,
   great scope, greatness, gush, heap, high tide, high water, hoard,
   hugeness, immensity, impletion, incessancy, infinity, intactness,
   integrity, intensity, inventory, jointlessness, landslide, larder,
   largeness, lavishness, liberality, liberalness, load, lots,
   luxuriance, magnitude, mass, material, materials, materiel,
   maximum, might, mightiness, monotony, more than enough, mountain,
   much, muchness, multitude, munitions, myriad, myriads,
   numerousness, ocean, oceans, opulence, opulency, outpouring,
   overflow, overfullness, peck, pile, plenteousness, plentifulness,
   plenty, plethora, power, prevalence, prodigality, prodigiousness,
   productiveness, profuseness, profusion, provisionment, provisions,
   quantities, quantity, rations, repertoire, repertory, repleteness,
   repletion, rich harvest, rich vein, richness, rick, riot,
   riotousness, satiety, saturation, saturation point, scads, sea,
   seamlessness, shower, smoothness, soundness, spate, spring tide,
   stability, stack, steadiness, steady state, stock, stock-in-trade,
   stockpile, store, stores, stream, strength, stupendousness,
   substantiality, substantialness, successiveness, superabundance,
   superfluity, supplies, supply on hand, surfeit, teemingness, tons,
   treasure, treasury, tremendousness, unbrokenness,
   undifferentiation, uniformity, unintermittedness,
   uninterruptedness, uninterruption, unrelievedness, vastness,
   volume, wealth, wholeness, world, worlds