parasite

American  

[par-uh-sahyt] / ˈpær əˌsaɪt /

noun

• parasites
  plural

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.

   Synonyms:

   hanger-on, sponge, leech, toady, sycophant

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

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parasite British  

/ ˈpærəˌsaɪt, ˌpærəˈsɪtɪk /

noun

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

3. (formerly) a sycophant

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parasite Scientific  

/ păr′ə-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.

2. ◆ 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.

3. ◆ 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.

4. See more at host

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parasite Cultural  

1. 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.

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Discover More

The term parasite is often applied to a person who takes advantage of other people and fails to offer anything in return.

Other Word Forms

Derived Forms

• parasitic
  adjective
• parasitically
  adverb

Inflected Forms

Nouns

• parasites
  plural

Etymology

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

Compare meaning

How does parasite compare to similar and commonly confused words? Explore the most common comparisons:

• parasite vs. parasitoid

Explanation

A creature that lives off another organism is a parasite. The parasite might not hurt the host, but it doesn't do anything to help it, either. If you call someone a parasite, you are really hurling an insult! The Ancient Greeks used the word parasitos to describe someone who ate at your table but never invited you back. Some telling synonyms include leech," toady, sponge, and hanger-on." Nice, huh? Some crafty birds, such as the cowbird or cuckoo, are called social parasites, laying their eggs in other birds' nests and expecting those mamas to raise their young for them. Unfortunately, there are some people like that, too.

Example Sentences

See Examples For:

parasite parasites

A produce lobby group asked U.S. health officials to change how they communicate about the recent parasite outbreak, citing sagging sales of fruit and vegetables.

From The Wall Street Journal ● Aug. 28, 2026

The infection, which is preventable and curable, is caused by a parasite and does not spread from person to person.

From BBC ● Aug. 26, 2026

These include threats to animal health, including the New World screwworm, a flesh-eating parasite.

From Barron's ● Aug. 21, 2026

And Taylor Farms would certainly top the list for anyone glued to a toilet bowl lately, thanks to the company’s alleged indiscretion handling lettuce laced with the “explosive diarrhea” parasite.

From Salon ● Aug. 19, 2026

“The parasite believes itself to be the host,” I said.

From "Turtles All the Way Down" by John Green

"One of my takeaway conclusions from the Science paper was that many Greenland sharks have parasites attached to their eyes -- which could impair their vision," she says.

From Science Daily ● Aug. 23, 2026

Handling wild game can pose food-safety risks: The Centers for Disease Control and Prevention warns that raw or undercooked wild game, including bear meat, can carry trichinella parasites, which cause trichinellosis.

From Salon ● Aug. 8, 2026

They’ve traveled by ground and plane, across seven different eastern U.S. states, for one purpose: to be tested for parasites, including cyclospora.

From The Wall Street Journal ● Aug. 5, 2026

A lab tests the mosquitoes for parasites and viruses.

From Slate ● Aug. 4, 2026

Unlike the viruses, they are not thoroughgoing parasites.

From "Cosmos" by Carl Sagan