hazardous

adjective

haz·​ard·​ous ˈha-zər-dəs How to pronounce hazardous (audio)
Synonyms of hazardous
1
: involving or exposing one to risk (as of loss or harm)
a hazardous occupation
disposing of hazardous waste
2
: depending on the effect of unpredictable and unanalyzable forces in determining events : depending on hazard (see hazard entry 1 sense 2a) or chance
hazardous outcomes
hazardously adverb
hazardousness noun

Synonyms of hazardous

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dangerous, hazardous, precarious, perilous, risky mean bringing or involving the chance of loss or injury.

dangerous applies to something that may cause harm or loss unless dealt with carefully.

soldiers on a dangerous mission

hazardous implies great and continuous risk of harm or failure.

claims that smoking is hazardous to your health

precarious suggests both insecurity and uncertainty.

earned a precarious living by gambling

perilous strongly implies the immediacy of danger.

perilous mountain roads

risky often applies to a known and accepted danger.

shied away from risky investments

Examples of hazardous in a Sentence

It was a hazardous voyage. These are hazardous chemicals that can cause death if inhaled.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The town could also consider lowering the current 80-foot height allowance and requiring plans to remove equipment and hazardous materials if a facility closes. — Nora O'Neill, Charlotte Observer, 4 Aug. 2026 The Environmental Protection Agency declared a 27-square-mile area within the city a hazardous waste zone, known as a Superfund site, after the American Smelting and Refining Company closed in the 1990s. — Cassandra Garibay, ProPublica, 4 Aug. 2026 To remove the metals, harsh chemicals are introduced, churning out piles of hazardous sludge in the process. — Mrigakshi Dixit, Interesting Engineering, 3 Aug. 2026 Wildfire smoke causing unhealthy conditions Much of the Northwest will remain under hazardous conditions this week, with gusty winds and high temperatures helping wildfires spread quickly. — Janet Loehrke, USA Today, 3 Aug. 2026 See All Example Sentences for hazardous

Word History

Etymology

see hazard entry 1

First Known Use

1549, in the meaning defined at sense 1

Time Traveler
The first known use of hazardous was in 1549

Rhymes for hazardous

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Browse Nearby Words

hazard lights
hazardous
hazardously
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Cite this Entry

“Hazardous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hazardous. Accessed 5 Aug. 2026.

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Kids Definition

hazardous

adjective
haz·​ard·​ous ˈhaz-ərd-əs How to pronounce hazardous (audio)
: dangerous sense 1, risky
hazardously adverb
hazardousness noun

Legal Definition

hazardous

adjective
haz·​ard·​ous
: creating a hazard : involving or exposing one to risk (as of loss or harm)
a hazardous occupation
a hazardous substance
hazardously adverb

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