Definition of contagious
1
: transmissible by direct or indirect contact with an infected person
contagious diseases contagious intestinal illness contagious skin rash contagious viruses
— see also contagious disease
2
: bearing contagion
contagious people
3
: used for contagious diseases
a contagious ward
4
: exciting similar emotions or conduct in others
contagious enthusiasm contagious laughter
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Merriam-Webster unabridged
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Time Traveler for contagious
The first known use of contagious was in the 14th century
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