[ par-uh-sahyt ]
See synonyms for: parasiteparasites on

  1. an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutriment.

  2. 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: They are greedy politicians, parasites with their snouts in the public trough.

  1. (in ancient Greece) a person who received free meals in return for amusing or impudent conversation, flattering remarks, etc.

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Origin of parasite

First recorded in 1530–40; from Latin parasītus, from Greek parásītos one who eats at another's table, originally an adjective: “feeding beside,” equivalent to para- + sît(os) “grain, food” + -os adjective suffix; see para-1

Other words for parasite

Words Nearby parasite Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use parasite in a sentence

British Dictionary definitions for parasite


/ (ˈpærəˌsaɪt) /

  1. 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

  2. a person who habitually lives at the expense of others; sponger

  1. (formerly) a sycophant

Origin of parasite

C16: via Latin from Greek parasitos one who lives at another's expense, from para- 1 + sitos grain

Derived forms of parasite

  • parasitic (ˌpærəˈsɪtɪk) or parasitical, adjective
  • parasitically, adverb

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

Scientific definitions for parasite


[ părə-sīt′ ]

  1. 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.

Cultural 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.

Notes for parasite

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.