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adjective del·e·te·ri·ous \ˌde-lə-ˈtir-ē-əs\

Simple Definition of deleterious

  • : damaging or harmful

Source: Merriam-Webster's Learner's Dictionary

Full Definition of deleterious

  1. :  harmful often in a subtle or unexpected way <deleterious effects> <deleterious to health>

deleteriously adverb
deleteriousness noun

Examples of deleterious in a sentence

  1. In developing countries, the imposition of boundaries around national parks and protected areas has been deleterious for both people and wildlife. —Kristin B. Gunther, Association of American Geographers, 2002

  2. Most everyone now knows the action of pressing mouse keys is far more deleterious to the tender structures of the wrist and hand than typing is. —Michael Finley, Albany (New York) Times-Union, 2 Sept. 1998

  3. This skewed allocation of resources away from those most in need, in turn, insures that many young people from low-income families will continue to be shut out of the economy, with obvious deleterious family and social consequences. —Iris C. Rotberg, Education Week, 9 Mar. 1994

  4. For as James Keirans pointed out to me, ticks are the world's most notorious carriers of the agents of diseases that strike animals, wild and domestic. And they rank second only to mosquitoes in their deleterious effect on humans. —Edwards Park, Smithsonian, January 1987

  5. The chemical is deleterious to the environment.

  6. The drug has no deleterious effects on patients.

Origin of deleterious

Greek dēlētērios, from dēleisthai to hurt

First Known Use: 1643

Synonym Discussion of deleterious

pernicious, baneful, noxious, deleterious, detrimental mean exceedingly harmful. pernicious implies irreparable harm done through evil or insidious corrupting or undermining <the claim that pornography has a pernicious effect on society>. baneful implies injury through poisoning or destroying <the baneful notion that discipline destroys creativity>. noxious applies to what is both offensive and injurious to the health of a body or mind <noxious chemical fumes>. deleterious applies to what has an often unsuspected harmful effect <a diet found to have deleterious effects>. detrimental implies obvious harmfulness to something specified <the detrimental effects of excessive drinking>.

Medical Dictionary


adjective del·e·te·ri·ous \ˌdel-ə-ˈtir-ē-əs\

Medical Definition of deleterious

  1. :  harmful often in a subtle or an unexpected way <the deleterious effects of radiation and chemotherapy on the marrow—Christine Gorman> <deleterious genes>

Seen and Heard

What made you want to look up deleterious? Please tell us where you read or heard it (including the quote, if possible).


to dishevel or rumple

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