a blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances which the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood.
early 20th century: from anti-+ body, translating German Antikörper, from anti- 'against' + Körper 'body'
antibody in other Oxford dictionaries
Definition of antibody in the US English dictionary