[par-uh-sahy-tiz-uh m, -si-]


Biology. a relation between organisms in which one lives as a parasite on another.
a parasitic mode of life or existence.
Pathology. a diseased condition due to parasites.
(in some totalitarian countries)
  1. unemployment or refusal to work.
  2. employment in work considered nonessential by the state.

Origin of parasitism

First recorded in 1605–15; parasite + -ism
Related formsnon·par·a·sit·ism, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for parasitism

Historical Examples of parasitism

British Dictionary definitions for parasitism



the relationship between a parasite and its host
the state of being infested with parasites
the state of being a parasite
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

Word Origin and History for parasitism

1610s, from parasite + -ism. Biological sense is from 1853.

Online Etymology Dictionary, © 2010 Douglas Harper

parasitism in Medicine


[părə-sĭ-tĭz′əm, -sī-]


A symbiotic relationship in which one species, the parasite, benefits at the expense of the other, the host.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

parasitism in Science



A relationship between two organisms in which one organism (the parasite) benefits and the other (the host) is harmed. Parasites derive nutrition from their host and may also gain other benefits such as shelter and a habitat in which to grow and reproduce. See more at parasite. Compare amensalism commensalism mutualism.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.