The Collaborative International Dictionary of English v.0.48:

Malassimilation \Mal`as*sim`i*la"tion\, n. [Mal- +
   assimilation.] (Physiol.)
   (a) Imperfect digestion of the several leading constituents
       of the food.
   (b) An imperfect elaboration by the tissues of the materials
       brought to them by the blood.
       [1913 Webster]