The Collaborative International Dictionary of English v.0.48:

Overmuch \O"ver*much"\, a.
   Too much. -- adv. In too great a degree; too much. -- n. An
   excess; a surplus.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overmuch
    adv 1: more than necessary; "she eats too much"; "let's not
           blame them overmuch" [syn: overmuch, too much]
    adj 1: very great in quantity; overabundant; "showed overmuch
           affection"
    n 1: a quantity that is more than what is appropriate; "four-
         year-olds have an overabundance of energy"; "we received an
         inundation of email" [syn: overabundance, overmuch,
         overmuchness, superabundance]

Moby Thesaurus II by Grady Ward, 1.0:

133 Moby Thesaurus words for "overmuch":
   a bit much, abandon, abandoned, boundless, boundlessness,
   egregious, egregiousness, enormous, enormousness, exaggerated,
   exaggeration, excess, excessive, excessively, excessiveness,
   exorbitance, exorbitancy, exorbitant, exorbitantly, extravagance,
   extravagancy, extravagant, extreme, extremely, extremes, extremism,
   extremity, fabulous, fabulousness, fancy, giantism, gigantic,
   gigantism, gluttonous, gluttony, high, hyperbole, hyperbolic,
   hypertrophied, hypertrophy, immensely, immoderacy, immoderate,
   immoderately, immoderateness, immoderation, incontinence,
   incontinent, inordinacy, inordinance, inordinate, inordinately,
   inordinateness, intemperance, intemperate, intemperately,
   intemperateness, lavish, monstrous, monstrousness, nimiety,
   out of bounds, out of sight, outrageous, outrageously,
   outrageousness, over, overabundance, overabundant, overbig,
   overbounteous, overcopious, overdeveloped, overdevelopment,
   overexuberant, overflow, overfull, overgenerous, overgreat,
   overgreatness, overgrown, overgrowth, overindulgence, overkill,
   overlarge, overlargeness, overlavish, overliberal, overluxuriant,
   overly, overmuchness, overnumerous, overplenteous, overplentiful,
   overplenty, overplus, overpopulated, overpopulous, overprolific,
   overweening, overweeningly, plentiful, plethora, plethoric,
   prodigal, pullulating, radicalism, riotous, steep, stiff,
   superabundant, superfluity, surfeit, surplus, surplusage, swarming,
   teeming, too, too much, too-muchness, too-too, unbridled,
   unconscionable, unconscionableness, unconscionably, undue,
   undueness, unduly, unreasonable, unreasonableness, unreasonably,
   unrestrained, unrestrainedness