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[par-uh-sahyt] /ˈpær əˌsaɪt/
an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutriment.
a person who receives support, advantage, or the like, from another or others without giving any useful or proper return, as one who lives on the hospitality of others.
(in ancient Greece) a person who received free meals in return for amusing or impudent conversation, flattering remarks, etc.
Origin of parasite
1530-40; < Latin parasītus < Greek parásītos one who eats at another's table, orig. adj.: feeding beside, equivalent to para- para-1 + sît(os) grain, food + -os adj. suffix
2. sycophant, toady, leech, sponge, hanger-on. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for parasite
Contemporary Examples
Historical Examples
  • Even were he an idler and a parasite and nothing worse, however, he has no claim to be tolerated.

    The Vagrancy Problem. William Harbutt Dawson
  • I worked hard, and had to give up what I earned to every kind of parasite.

    Waiting for Daylight Henry Major Tomlinson
  • By and by there appear somewhere in the parasite those specks of black pigment which we saw in the mature animal.

  • Since the dead did not wish him to be a man, he would be a parasite.

    The Dead Command Vicente Blasco Ibez
  • The mouth parts form a short piercing beak with which the parasite sucks the blood of its host.

    The Life of Crustacea William Thomas Calman
  • Man has always been a parasite; always he had to live on the works of others.

    The Last Evolution John Wood Campbell
British Dictionary definitions for parasite


an animal or plant that lives in or on another (the host) from which it obtains nourishment. The host does not benefit from the association and is often harmed by it
a person who habitually lives at the expense of others; sponger
(formerly) a sycophant
Derived Forms
parasitic (ˌpærəˈsɪtɪk), parasitical, adjective
parasitically, adverb
Word Origin
C16: via Latin from Greek parasitos one who lives at another's expense, from para-1 + sitos grain
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
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Word Origin and History for parasite

1530s, "a hanger-on, a toady, person who lives on others," from Middle French parasite (16c.) or directly from Latin parasitus "toady, sponger," and directly from Greek parasitos "one who lives at another's expense, person who eats at the table of another," from noun use of an adjective meaning "feeding beside," from para- "beside" (see para- (1)) + sitos "food," of unknown origin. Scientific meaning "animal or plant that lives on others" is first recorded 1640s (implied in parasitical).

Online Etymology Dictionary, © 2010 Douglas Harper
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parasite in Medicine

parasite par·a·site (pār'ə-sīt')

  1. An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of its host.

  2. In conjoined twins, the usually incomplete twin that derives its support from the more nearly normal fetus.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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parasite in Science
An organism that lives on or in a different kind of organism (the host) from which it gets some or all of its nourishment. Parasites are generally harmful to their hosts, although the damage they do ranges widely from minor inconvenience to debilitating or fatal disease. ◇ A parasite that lives or feeds on the outer surface of the host's body, such as a louse, tick, or leech, is called an ectoparasite. Ectoparasites do not usually cause disease themselves although they are frequently a vector of disease, as in the case of ticks, which can transmit the organisms that cause such diseases as Rocky Mountain spotted fever and Lyme disease. ◇ A parasite that lives inside the body of its host is called an endoparasite. Endoparasites include organisms such as tapeworms, hookworms, and trypanosomes that live within the host's organs or tissues, as well as organisms such as sporozoans that invade the host's cells. See more at host.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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parasite in Culture

parasite definition

An organism that lives off or in another organism, obtaining nourishment and protection while offering no benefit in return. Human parasites are often harmful to the body and can cause diseases, such as trichinosis.

Note: The term parasite is often applied to a person who takes advantage of other people and fails to offer anything in return.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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