The Collaborative International Dictionary of English v.0.48:

Disaggregation \Dis*ag`gre*ga"tion\
   (d[i^]s*[a^]g`gr[-e]*g[=a]"sh[u^]n), n. [Cf. F.
   d['e]sagr['e]gation.]
   The separation of an aggregate body into its component parts.
   [1913 Webster]