The Collaborative International Dictionary of English v.0.48:

Dissunder \Dis*sun"der\, v. t. [imp. & p. p. Dissundered; p.
   pr. & vb. n. Dissundering.] [Pref. dis- (intens) + sunder.]
   To separate; to sunder; to destroy. [R.] --Chapman.
   [1913 Webster]