parasitism

noun par·a·sit·ism \ ˈper-ə-sə-ˌti-zəm , -ˌsī- , ˈpa-rə- \

Updated on: 22 Apr 2018

Definition of parasitism

1 : the behavior of a parasite

2 : an intimate association between organisms of two or more kinds; especially : one in which a parasite obtains benefits from a host which it usually injures

3 : parasitosis

See parasitism defined for kids

Recent Examples of parasitism from the Web

Hauber studies a behavior known as brood parasitism, in which birds lay eggs in the nests of other species, leaving the unwitting foster parents to rear their chicks.

— matt warren, Science | AAAS, "Here’s what happens when you replace toads and turtles with 3D-printed replicas in the wild," 17 Apr. 2018
As to why warblers and other victims of brood parasitism fail to retaliate by themselves evolving thicker eggshells, and thus faster-hatching young, that is unclear.

— The Economist, "Convergent evolutionThicker eggshells help cuckoos hatch earlier than their nestmates," 18 Jan. 2018
This looks like a classic case of convergent evolution, but no one has been able to prove the point by demonstrating a benefit derived from it that is connected directly with brood parasitism.

— The Economist, "Convergent evolutionThicker eggshells help cuckoos hatch earlier than their nestmates," 18 Jan. 2018
Such brood parasitism has arisen independently at least three times, in the groups known as cuckoos, cowbirds and honeyguides.

— The Economist, "Convergent evolutionThicker eggshells help cuckoos hatch earlier than their nestmates," 18 Jan. 2018
The cowbird practice of brood parasitism can, and has, had serious implications for other native birds.

— taylor piephoff, charlotteobserver, "Cowbirds make other species raise their chicks, neglecting their own," 30 June 2017
After all, such complex parasitism is serious evolutionary trickery.

— matt simon, WIRED, "Absurd Creature of the Week: This Mussel Does an Incredible Impression of a Fish," 16 Oct. 2015
Some endangered or threatened species populations have been adversely affected by cowbird parasitism to the point where cowbird trapping programs have been implemented.

— taylor piephoff, charlotteobserver, "Cowbirds make other species raise their chicks, neglecting their own," 30 June 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'parasitism.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of parasitism

circa 1611

Other Ecology Terms

Malthusian, anthropogenic, biomass, carbon footprint, crepuscular, niche, sere, symbiosis, taiga, tundra

Medical Dictionary

parasitism

noun par·a·sit·ism \ ˈpar-ə-sə-ˌtiz-əm , -ˌsīt-ˌiz- \

medical Definition of parasitism

1 : an intimate association between organisms of two or more kinds; especially : one in which a parasite obtains benefits from a host which it usually injures

2 : parasitosis