Definition of "infectious" in English

adjective

1. (pathology, of an illness) Caused by an agent that enters the host's body (such as a bacterium, virus, parasite, or prion); often, also, transmitted among hosts via any of various routes (for example, contact, droplet-borne, airborne, waterborne, foodborne, fomite-borne, or bloodborne).

   • Cancer is usually not infectious.
   • More infectious diseases like the flu are usually less potent.

2. (pathology, typically of a person) Able to infect others; capable of transmitting pathogens.

   • Despite feeling better, the patient is still infectious.

3. (of feelings and behaviour) Spreading quickly from one person to another.

   • infectious smile
   • Her enthusiasm for work can be really infectious.

4. (informal) Memorable and invoking excitement or interest.

   • Pop music is more infectious than elevator music.