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

Synonyms for parasite Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for parasite

Contemporary Examples of parasite

Historical Examples of parasite

  • He ceased for a time at least to be a gentleman to become a hanger-on, a parasite once more.

    Albert Durer

    T. Sturge Moore

  • Parasiticus means a parasite; so called because it grows on a Scleroderma.

  • To be proud that one wasn't a loafer or a drone, or a parasite on the body economic.

    Mixed Faces

    Roy Norton

  • And you can't understand that I am precisely what you've described--a parasite!


    Louis Joseph Vance

  • It is an unaccountable prejudice that makes the parasite unpopular.

    One Of Them

    Charles James Lever

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 Formsparasitic (ˌpærəˈsɪtɪk) or parasitical, adjectiveparasitically, adverb

Word Origin for parasite

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

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

Medicine definitions for parasite




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

Science definitions for parasite



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 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Culture definitions for parasite


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.


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