Definition of infectious
1a : producing or capable of producing infection bacteria and other infectious agents
b : caused by or resulting from an infection with one or more pathogenic agents
infectious mononucleosis — see also infectious disease
c : transmitting or capable of transmitting infection : containing pathogenic agents which may be transmitted
infectious droplets
2 : spreading or capable of spreading rapidly to others
an infectious laugh Her happiness was infectious.
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Time Traveler for infectious
The first known use of infectious was in 1534
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