The Collaborative International Dictionary of English v.0.48:

assimilating \assimilating\ adj.
   tending to or characterized by or causing assimilation (being
   absorbed into or incorporated).

   Syn: assimilative, assimilatory.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Assimilate \As*sim"i*late\, v. t. [imp. & p. p. Assimilated;
   p. pr. & vb. n. Assimilating.] [L. assimilatus, p. p. of
   assimilare; ad + similare to make like, similis like. See
   Similar, Assemble, Assimilate.]
   1. To bring to a likeness or to conformity; to cause a
      resemblance between. --Sir M. Hale.
      [1913 Webster]

            To assimilate our law to the law of Scotland. --John
                                                  Bright.
      [1913 Webster]

            Fast falls a fleecy; the downy flakes
            Assimilate all objects.               --Cowper.
      [1913 Webster]

   2. To liken; to compa?e. [R.]
      [1913 Webster]

   3. To appropriate and transform or incorporate into the
      substance of the assimilating body; to absorb or
      appropriate, as nourishment; as, food is assimilated and
      converted into organic tissue.
      [1913 Webster]

            Hence also animals and vegetables may assimilate
            their nourishment.                    --Sir I.
                                                  Newton.
      [1913 Webster]

            His mind had no power to assimilate the lessons.
                                                  --Merivale.
      [1913 Webster]

WordNet (r) 3.0 (2006):

assimilating
    adj 1: capable of taking (gas, light, or liquids) into a
           solution; "an assimilative substance [syn:
           assimilating, assimilative, assimilatory]