Definition of serum noun from the Oxford Advanced Learner's Dictionary

     

    serum

     noun
    noun
    BrE BrE//ˈsɪərəm//
     
    ; NAmE NAmE//ˈsɪrəm//
     
    (pl. sera
    BrE BrE//ˈsɪərə//
     
    ; NAmE NAmE//ˈsɪrə//
     
    , serums)
     
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  1. 1[uncountable] (biology) the thin liquid that remains from blood when the rest has clotted
  2. 2[uncountable, countable] (medical) serum taken from the blood of an animal and given to people to protect them from disease, poison, etc. snakebite serum
  3. 3[uncountable] any liquid like water in body tissue
  4. Word Origin late 17th cent.: from Latin, literally ‘whey’.
See the Oxford Advanced American Dictionary entry: serum