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: Webster's Revised Unabridged Dictionary (1913)