The Collaborative International Dictionary of English v.0.48:

Abnormous \Ab*nor"mous\, a. [L. abnormis; ab + norma rule. See
   Normal.]
   Abnormal; irregular. --Hallam.
   [1913 Webster]

         A character of a more abnormous cast than his equally
         suspected coadjutor. --State Trials.
   [1913 Webster]