/ ɪnˈfekʃəs; NAmE / adjective
1.
an infectious disease can be passed easily from one person to another, especially through the air they breathe :
Flu is highly infectious.
( figurative )
infectious laughter
2.
[ not usually before noun ] if a person or an animal is infectious , they have a disease that can be spread to others :
I'm still infectious.
—compare contagious
► in·fec·tious·ly adverb :
to laugh infectiously
► in·fec·tious·ness noun [ U ]
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WORD ORIGIN
mid 16th cent.: from infection + -ous .