The Collaborative International Dictionary of English v.0.48:

Disacknowledge \Dis`ac*knowl"edge\, v. t. [imp. & p. p.
   Disacknowledged; p. pr. & vb. n. Disacknowledging.]
   To refuse to acknowledge; to deny; to disown. [Obs.] --South.
   [1913 Webster]