Definition of contagious adjective from the Oxford Advanced Learner's Dictionary

     

    contagious

     adjective
    adjective
    BrE BrE//kənˈteɪdʒəs//
     
    ; NAmE NAmE//kənˈteɪdʒəs//
     
    Ailments and diseases, Being ill
     
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  1. 1a contagious disease spreads by people touching each other Scarlet fever is highly contagious. (figurative) His enthusiasm was contagious (= spread quickly to other people). a contagious laugh The new disease proved contagious. See related entries: Ailments and diseases, Being ill
  2. 2[not usually before noun] if a person is contagious, they have a disease that can be spread to other people by touch
  3. compare infectious
    Word Origin late Middle English: from late Latin contagiosus, from contagio, from con- ‘together with’ + the base of tangere ‘to touch’.
See the Oxford Advanced American Dictionary entry: contagious