WordWeb Online

1. Caused by infection or capable of causing infection
   "viruses and other infectious agents";
   - infective
    
2. Easily spread
   "fear is exceedingly infectious; children catch it from their elders"
    
3. Of or relating to infection
   "infectious hospital"; "infectious disease"

See also: catching, communicable, contagious, contaminating, contractable, corrupting, infected, septic, transmissible, transmittable

Antonym: noninfectious

Encyclopedia: Infectious