The Collaborative International Dictionary of English v.0.48:

Dizzard \Diz"zard\ (d[i^]z"z[~e]rd), n. [See Dizzy, and cf.
   Disard.]
   A blockhead. [Obs.] [Written also dizard, and disard.] --
   Diz"zard*ly, adv. [Obs.]
   [1913 Webster]