infectious
Americanadjective
-
communicable by infection, as from one person to another or from one part of the body to another.
infectious diseases.
- Synonyms:
- catching
-
causing or communicating infection.
-
tending to spread from one to another.
infectious laughter.
-
Law. capable of contaminating with illegality; exposing to seizure or forfeiture.
-
Obsolete. diseased.
adjective
-
(of a disease) capable of being transmitted Compare contagious
-
(of a disease) caused by microorganisms, such as bacteria, viruses, or protozoa
-
causing or transmitting infection
-
tending or apt to spread, as from one person to another
infectious mirth
-
international law
-
tainting or capable of tainting with illegality
-
rendering liable to seizure or forfeiture
-
Related Words
See contagious.
Other Word Forms
- infectiously adverb
- infectiousness noun
- noninfectious adjective
- noninfectiously adverb
- noninfectiousness noun
- uninfectious adjective
- uninfectiously adverb
- uninfectiousness noun
Etymology
Origin of infectious
First recorded in 1535–45; infect(ion) + -ious
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The infectious track about owning your own power has been climbing up the charts and popping up on social media feeds thanks to its dance trend.
From BBC • Apr. 8, 2026
Dr. Amesh Adalja, an infectious disease expert and senior scholar at Johns Hopkins Center for Health Security, told Salon he is not hopeful the outbreaks can be contained at this point.
From Salon • Apr. 8, 2026
After hours cooling his heels, Kornev is then informed that Stepniak is ill with an infectious disease — come back another time.
From Los Angeles Times • Mar. 26, 2026
They had no manual on how to handle an infectious disease at 40,000 feet, and they lacked the basics, including personal protective equipment for the crew.
From The Wall Street Journal • Mar. 20, 2026
When the belted crates of art started arriving at the museum, Dr. Lange’s enthusiasm was infectious.
From "Salt to the Sea" by Ruta Sepetys
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
