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