Source : Webster's Revised Unabridged Dictionary (1913)

Antibody \An"ti*bod`y\, n. (Physiol. Chem.)
   Any of various bodies or substances in the blood which act in
   antagonism to harmful foreign bodies, as toxins or the
   bacteria producing the toxins. Normal blood serum apparently
   contains variousantibodies, and the introduction of toxins or
   of foreign cells also results in the development of their
   specific antibodies.

Source : WordNet®

antibody
     n : any of a large variety of proteins normally present in the
         body or produced in response to an antigen which it
         neutralizes, thus producing an immune response