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

People contract the illness by consuming food or water contaminated with the feces of an infected person that contained the parasite.

From Los Angeles Times ● Jul. 14, 2026

People can get sick with cyclosporiasis after drinking water or eating food that’s contaminated with the parasite.

From MarketWatch ● Jul. 14, 2026

Health officials are searching for the path of a parasite that has sickened potentially thousands of people across more than 30 states and isn’t showing signs of stopping.

From The Wall Street Journal ● Jul. 14, 2026

Some experts told the BBC that the parasite is notoriously difficult to trace, a task possibly complicated in part by cuts to federal health agencies.

From BBC ● Jul. 14, 2026

Then a parasite of the scale insect was imported from Australia, a small lady beetle called the vedalia.

From "Silent Spring" by Rachel Carson

"The doctor sat me down and said, 'right, okay, we've looked at your scans and we've found 38 parasites on your brain'," said Lowri.

From BBC ● Jun. 30, 2026

The injectable drug can be used along with a one-dose topical spray that kills the parasites at a cost of about 30 cents per animal, he said.

From MarketWatch ● Jun. 10, 2026

Left untreated, the infestation can be deadly, and the parasites can quickly spread.

From Barron's ● Jun. 4, 2026

“The Spartans might be . . . viewed as parasites, feeding off the forced labor of their helots,” he opines.

From The Wall Street Journal ● May 25, 2026

There will be no foul weather, or any parasites to hassle them, or any weeds to compete with for soil or nutrients.

From "The Martian" by Andy Weir