Source : Webster's Revised Unabridged Dictionary (1913)

Disproportional \Dis`pro*por"tion*al\, a.
   Not having due proportion to something else; not having
   proportion or symmetry of parts; unsuitable in form, quantity
   or value; inadequate; unequal; as, a disproportional limb
   constitutes deformity in the body; the studies of youth
   should not be disproportional to their understanding.

Source : WordNet®

disproportional
     adj : out of proportion [syn: {disproportionate}] [ant: {proportionate}]