The Collaborative International Dictionary of English v.0.48:

Abnormity \Ab*nor"mi*ty\, n.; pl. Abnormities. [LL.
   abnormitas. See Abnormous.]
   Departure from the ordinary type; irregularity; monstrosity.
   "An abnormity . . . like a calf born with two heads." --Mrs.
   Whitney.
   [1913 Webster]