: any of a large number of proteins of high molecular weight that are produced normally by specialized B cells after stimulation by an antigen and act specifically against the antigen in an immune response, that are produced abnormally by some cancer cells, and that typically consist of four subunits including two heavy chains and two light chains called also immunoglobulin Solo travelers and families can enter the country only with special permission and are required to quarantine for at least 10 days unless an antibody test shows they are protected from the virus. Previous infection can easily be verified with the university’s own records of testing throughout the past school year, a positive viral test from another provider or an antibody test, which would prove either natural immunity or vaccination. Her Covid-19 test was negative last fall after some teammates and coaches at her gym tested positive, but in February an antibody test ordered by her pediatrician confirmed she had been infected with Covid-19. The researchers analyzed data on 39,086 people who were confirmed to have Covid-19 between March 2020 and January 2021, and had at least one antibody test performed with Labcorp after testing positive for the coronavirus infection. And another started reverse-engineering a live virus from the sequence, letting colleagues around the world know that the first steps towards developing an antibody test were already underway. Americans who can prove they are fully vaccinated, have an antibody test showing sufficient antibodies or proof of testing positive for COVID more than 15 days prior to arrival can bypass quarantine. These example sentences are selected automatically from various online news sources to reflect current usage of the word \'antibody.\' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback. First Known Use of antibody 1894, in the meaning defined above Post the Definition of antibody to Facebook Share the Definition of antibody on Twitter Cite this EntryAntibody. Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/antibody. Accessed 15 Aug. 2021. Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/antibody. Accessed 15 Aug. 2021.\">MLA Merriam-Webster.com Dictionary, s.v. antibody, accessed August 15, 2021, https://www.merriam-webster.com/dictionary/antibody.\">Chicago Merriam-Webster.com dictionary. Retrieved August 15, 2021, from https://www.merriam-webster.com/dictionary/antibody\">APA Merriam-Webster.com Dictionary, https://www.merriam-webster.com/dictionary/antibody. Accessed 8/15/2021.\">Merriam-Webster : a substance produced by special cells of the body that counteracts the effects of a disease germ or its poisons : any of a large number of proteins of high molecular weight that are produced normally by specialized B cells after stimulation by an antigen and act specifically against the antigen in an immune response, that are produced abnormally by some cancer cells, and that typically consist of four subunits including two heavy chains and two light chains called also immunoglobulin Love words? Need even more definitions? Subscribe to America\'s largest dictionary and get thousands more definitions and advanced search ad free! Merriam-Webster unabridged