infectious

[ in-fek-shuhs ]
/ ɪnˈfɛk ʃəs /

adjective

communicable by infection, as from one person to another or from one part of the body to another: infectious diseases.
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.

Origin of infectious

First recorded in 1535–45; infect(ion) + -ious

Related forms

Can be confused

contagious infectious (see synonym study at contagious)

Synonym study

1. See contagious.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for infectious

British Dictionary definitions for infectious

infectious

/ (ɪnˈfɛkʃəs) /

adjective

(of a disease) capable of being transmittedCompare 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 anotherinfectious mirth
international law
  1. tainting or capable of tainting with illegality
  2. rendering liable to seizure or forfeiture

Derived Forms

infectiously, adverbinfectiousness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for infectious

infectious

[ ĭn-fĕkshəs ]

adj.

Capable of causing infection.
Caused by or capable of being transmitted by infection.
Caused by a pathogenic microorganism or agent.

Related forms

in•fectious•ness n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for infectious

infectious

[ ĭn-fĕkshəs ]

Capable of causing infection. See Note at contagious.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.