The Collaborative International Dictionary of English v.0.48:

Decomposable \De`com*pos"a*ble\, a.
   Capable of being resolved into constituent elements.
   [1913 Webster]

WordNet (r) 3.0 (2006):

decomposable
    adj 1: capable of being partitioned [syn: analyzable,
           decomposable]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "decomposable":
   ablative, biodegradable, corrosive, decomposing, degradable,
   dilapidated, disintegrable, disintegrated, disintegrating,
   disintegrative, disjunctive, disruptive, erosive, moldering,
   putrefiable, putrescible, ravaged, resolvent, ruinous, separative,
   solvent, worn