From The Collaborative International Dictionary of English v.0.48:

combinatory \combinatory\ adj.
   1. same as combinatorial, 1.

   Syn: combinative, combinatorial.
        [WordNet 1.5]

   2. able to be combined.

   Syn: combinable, combinational, combining(prenominal).
        [WordNet 1.5]

   3. same as combinatorial, 2. [Narrower terms: combinative
      (vs. noncombinative)]

   Syn: combinatorial.
        [WordNet 1.5]

From The Collaborative International Dictionary of English v.0.48:

combinatorial \combinatorial\ combinatory \combinatory\adj.
   1. able to combine; tending to combine.

   Note: same as combinative, 2. [Narrower terms: integrative
         (vs. disintegrative)]

   Syn: combinative.
        [WordNet 1.5]

   2. of or relating to combinations. [Narrower terms:
      combinative (vs. noncombinative)] WordNet 1.5]

   3. produced by a process of combining; as, a combinatorial
      explosion of possibilities; -- used especially in
      reference to mathematical or statistical processes of
      computing possible combinations.
      PJC]

From WordNet (r) 2.0:

combinatory
     adj 1: marked by or relating to or resulting from combination [syn:
             combinative] [ant: noncombinative]
     2: relating to or involving combinations [syn: combinative, combinatorial]
     3: able to or tending to combine [syn: combinable, combinational]