parasite

noun

par·​a·​site ˈper-ə-ˌsīt How to pronounce parasite (audio)
ˈpa-rə-
plural parasites
1
: an organism living in, on, or with another organism in order to obtain nutrients, grow, or multiply often in a state that directly or indirectly harms the host (see host entry 1 sense 2a)
Now the death of its host is certainly a setback to any parasite. To some (like the tapeworm) it is fatal; but smarter ones (like the louse) simply go off in search of a new host.David Jones
The fungus is an obligate parasite, that is, it must have a living host (tobacco) on which to grow and complete its life cycle.G. B. Lucas
The blood schizogonic cycle of human malaria parasites has thus far been the most exhaustively studied phase of parasite development.Dominique Mazier et al.
Sadly, the vireo is vulnerable to a nest parasite, the brown-headed cowbird … . The cowbird lays its much-larger eggs in the vireo's nest, which hatch first and place such a high food demand on its tiny "parents" that the vireo young go unfed.Karen D. Fishler

Note: Some restrict the use of parasite to include only multicellular forms (such as protozoans and helminths) while others use it to include bacteria and viruses.

Unlike bacteria or viruses, parasites undergo a metamorphosis during their life cycles that presents the human immune system with a moving target.Lawrence M. Fisher
Like all viruses, the human immunodeficiency virus (HIV) is an intracellular parasite: the virus particle itself is inert and cannot propagate or do any damage until it enters a host cell.Jonathan N. Weber and Robin A. Weiss
Salmonella species are intracellular parasites, and it is thought that these bacteria gain access to their host by penetrating through intestinal epithelial cells.B. Brett Finlay et al.
see also ectoparasite, endoparasite
2
: someone or something that resembles a biological parasite in living off of, being dependent on, or exploiting another while giving little or nothing in return
But the frequent and familiar companions of the great, are those parasites, who practise the most useful of all arts, the art of flattery …Edward Gibbon
Their lyrics … convey a bilious contempt for the city's wealthy parasitesPhilip Montoro
In their view, the country is afflicted with a class of parasites—"Career politicians," who devote their lives to perpetuating themselves in office by spending the people's money.Hendrick Hertzberg
Regulatory agencies have stripped Holyfield of his boxing license now, protecting him from his pride and from the parasites who can still squeeze money out of the faded neon in his name.Dan Le Batard
Choose the Right Synonym for parasite

parasite, sycophant, toady, leech, sponge mean a usually obsequious flatterer or self-seeker.

parasite applies to one who clings to a person of wealth, power, or influence or is useless to society.

a jet-setter with an entourage of parasites

sycophant adds to this a strong suggestion of fawning, flattery, or adulation.

a powerful prince surrounded by sycophants

toady emphasizes the servility and snobbery of the self-seeker.

cultivated leaders of society and became their toady

leech stresses persistence in clinging to or bleeding another for one's own advantage.

a leech living off his family and friends

sponge stresses the parasitic laziness, dependence, and opportunism of the cadger.

a shiftless sponge, always looking for a handout

Examples of parasite in a Sentence

Many diseases are caused by parasites. She's a parasite who only stays with him for the money. These new companies are parasites feeding off the success of those who spent the last decade establishing the industry.
Recent Examples on the Web The deer also can get sick from eating food meant for humans and become vulnerable to parasites. Gwen Filosa, Miami Herald, 6 Feb. 2024 Experts say co-sleeping with your pet can have some downsides, including allergies, the risk of getting parasites, and potential sleep disruptions. Alyssa Hui, Health, 3 Feb. 2024 Until recently, it was thought that only organisms like viruses, bacteria, fungi, and parasites functioned as pathogens. Erin Prater, Fortune Well, 26 Jan. 2024 That’s why a group of parasite experts has developed a conservation plan for parasites. Avery Hurt, Discover Magazine, 22 Jan. 2024 Until recently, it was thought that only organisms like viruses, bacteria, fungi, and parasites were able to cause infections. Erin Prater, Fortune Well, 1 Feb. 2024 Also, be sure to budget for health care maintenance items like preventatives for heartworms, intestinal parasites, fleas and ticks. Laurie Larsh, Charlotte Observer, 30 Jan. 2024 But, alas, my body has repeatedly rejected the alien parasite, for reasons unknown. Leila Cobo, Billboard, 25 Jan. 2024 Modest landscape use is crucial to success, as too much or too little maintenance increases the butterflies’ vulnerability to parasites. Cameron Pugh, The Christian Science Monitor, 16 Jan. 2024 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'parasite.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Middle French, from Latin parasitus, from Greek parasitos, from para- + sitos grain, food

First Known Use

1539, in the meaning defined at sense 2

Time Traveler
The first known use of parasite was in 1539

Dictionary Entries Near parasite

Cite this Entry

“Parasite.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/parasite. Accessed 24 Feb. 2024.

Kids Definition

parasite

noun
par·​a·​site ˈpar-ə-ˌsīt How to pronounce parasite (audio)
1
: a person who lives at the expense of another
2
: a living thing which lives in or on another living thing in parasitism
3
: a person dependent on something else for life or support without making proper return

Medical Definition

parasite

noun
par·​a·​site ˈpar-ə-ˌsīt How to pronounce parasite (audio)
: an organism living in, with, or on another organism in order to obtain nutrients, grow, or multiply often in a state that directly or indirectly harms the host (see host sense 1)
The blood schizogonic cycle of human malaria parasites has thus far been the most exhaustively studied phase of parasite development.Dominique Mazier et al., Nature

Note: Some restrict the use of parasite to include only multicellular forms (such as protozoans and helminths) while others use it to include bacteria and viruses.

These cells call up a portion of the immune system that identifies and destroys cells infected with bacteria, viruses, and parasites.L. Seachrist, Science News
Like all viruses, the human immunodeficiency virus (HIV) is an intracellular parasite: the virus particle itself is inert and cannot propagate or do any damage until it enters a host cell.Jonathan N. Weber and Robin A. Weiss, Scientific American
Salmonella species are intracellular parasites, and it is thought that these bacteria gain access to their host by penetrating through intestinal epithelial cells.B. Brett Finlay et al., Science

More from Merriam-Webster on parasite

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