Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

  

English definition of “infectious”

infectious

adjective [not gradable]    /ɪnˈfek·ʃəs/
able to infect someone: infectious diseases If something is infectious, it quickly spreads or influences others: an infectious laugh
(Definition of infectious adjective from the Cambridge Academic Content Dictionary © Cambridge University Press)
Focus on the pronunciation of infectious

Definitions of “infectious” in other dictionaries

Word of the Day

sail

When a boat or a ship sails, it travels on the water.

Word of the Day

Blog

Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More