The Collaborative International Dictionary of English v.0.48:

Disproportionate \Dis`pro*por"tion*ate\, a.
   Not proportioned; unsymmetrical; unsuitable to something else
   in bulk, form, value, or extent; out of proportion;
   inadequate; as, in a perfect body none of the limbs are
   disproportionate; it is wisdom not to undertake a work
   disproportionate means. -- Dis`pro*por"tion*ate*ly, adv. --
   Dis`pro*por"tion*ate*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disproportionate
    adj 1: out of proportion [syn: disproportionate,
           disproportional] [ant: proportionate]
    2: not proportionate

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "disproportionate":
   abnormal, absurd, aggrandized, aimless, amorphous, amplified,
   anomalous, antagonistic, antipathetic, asymmetric, asymmetrical,
   at cross-purposes, at loggerheads, at odds, at variance, at war,
   ballyhooed, capricious, casual, clashing, contradictory, contrary,
   cranky, cross, desultory, differing, disaccordant, disagreeable,
   disagreeing, disarticulated, discontinuous, discordant, discrepant,
   disharmonious, disjunct, disordered, disparate, dispersed,
   dissident, dissimilar, dissonant, divergent, erratic, exaggerated,
   excessive, exorbitant, extravagant, extreme, fitful, formless,
   frivolous, grandiloquent, grating, gratuitous, haphazard,
   high-flown, hit-or-miss, hostile, hyperbolic, ill-matched,
   ill-sorted, immethodical, immiscible, inaccordant, inadequate,
   inchoate, incoherent, incommensurable, incommensurate,
   incompatible, incongruous, inconsequent, inconsistent, inconsonant,
   indiscriminate, inflated, inharmonious, inordinate, insufficient,
   irreconcilable, irregular, jangling, jarring, lopsided, magnified,
   meaningless, mismatched, misshapen, negative, nonsymmetrical,
   nonsystematic, nonuniform, odd, off-balance, orderless,
   out of accord, out of proportion, out of whack, overbalanced,
   overdone, overdrawn, overemphasized, overemphatic, overestimated,
   overgreat, overlarge, overpraised, oversold, overstated,
   overstressed, overwrought, oxymoronic, paradoxical, planless,
   prodigal, profuse, promiscuous, puffed, random, repugnant,
   self-contradictory, senseless, shapeless, skew, skewed, spasmodic,
   sporadic, straggling, straggly, stretched, superlative, systemless,
   touted, unarranged, unbalanced, unclassified, uncongenial,
   undirected, unequal, uneven, unfair, ungraded, unharmonious,
   unjoined, unmethodical, unordered, unorganized, unsorted,
   unsymmetrical, unsystematic, ununiform, vague, variant,
   wandering