pernicious
(Formal)
[adjective]
Synonyms: wicked, bad, damaging, dangerous, deadly, destructive, detrimental, evil, fatal, harmful, hurtful, malign, poisonous

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Antonyms: innocuous
Contrasted words: harmless, uninjurious, nonmalignant, nonpoisonous, nontoxic
Related Words: damaging, deleterious, detrimental, harmful, hurtful, baleful, malefic, maleficent, malign, sinister, miasmatic, miasmic, poisonous, toxic, venomous, malignant, swart, virulent, destructive, devastating, ruinous, fatal, killing, lethal, mortal

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English Thesaurus: harmful, be bad for somebody/something, damaging, detrimental, negative, ...

[TahlilGaran] English Synonym Dictionary ▲

per‧ni‧cious /pəˈnɪʃəs $ pər-/ adjective formal
[Date: 1500-1600; Language: French; Origin: pernicieux, from Latin perniciosus, from pernicies 'destruction', from nex 'violent death']
very harmful or evil, often in a way that you do not notice easily:
the pernicious effects of poverty
the media’s pernicious influence
—perniciously adverb

[TahlilGaran] Dictionary of Contemporary English ▲

harmful causing physical harm – used especially about things that cause harm to your health, the environment etc:
Smoking is harmful to your health.
drugs with harmful side-effects
be bad for somebody/something to have a harmful effect on someone or something. This phrase is very commonly used in everyday English when saying that something is harmful:
Everyone knows that too much alcohol is bad for you.
damaging used about things that cause permanent physical harm, or that have a bad effect in other ways, for example on people’s opinion of someone:
Acid rain has a damaging effect on trees and the soil.
The allegations were very damaging to his career.
Constant criticism is damaging to a child’s self-esteem.
detrimental formal causing harm or having a bad effect on something:
Employers are worried that the new laws will have a detrimental effect on their business.
chemicals that are detrimental to the environment
policies that have been detrimental to the interests of old people
negative a negative effect is one that is bad and causes problems:
The car tax had a negative effect on car sales.
the negative impact of the recession in the US
hazardous hazardous substances are likely to be dangerous to people’s health and safety:
Hazardous waste needs to be disposed of safely.
hazardous chemicals
toxic toxic substances, smoke etc are poisonous:
toxic waste
toxic fumes
Toxic chemicals spilled into the river.
pernicious /pəˈnɪʃəs $ pər-/ formal used about something that has a gradual bad effect which is not easy to notice, especially on people’s morals, or on their health:
the pernicious effects of violent video games
the pernicious effect of secondhand smoke

[TahlilGaran] English Thesaurus ▲