haz·​ard·​ous ˈha-zər-dəs How to pronounce hazardous (audio)
: involving or exposing one to risk (as of loss or harm)
a hazardous occupation
disposing of hazardous waste
: 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
Choose the Right Synonym for hazardous

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

Example Sentences

It was a hazardous voyage. These are hazardous chemicals that can cause death if inhaled.
Recent Examples on the Web This may result in hazardous driving conditions due to limited visibilities and a potential for slippery roadways. oregonlive, 17 Nov. 2022 The falling snow will lead to reduced visibility and hazardous driving conditions today. Jennifer Gray, CNN, 14 Nov. 2022 By Tuesday night, snow levels could drop to around 5,000 feet, creating potentially hazardous conditions along the Tejon Pass on the 5 Freeway and the Soledad Pass on the 14 Freeway between Santa Clarita and Palmdale, meteorologists said. Los Angeles Times, 8 Nov. 2022 High winds in the Matanuska Valley and Valdez area caused hazardous driving conditions Saturday while multiple power outages were reported in the Eagle River-Chugiak area. Annie Berman, Anchorage Daily News, 6 Nov. 2022 The combination of strong winds and heavy rain will produce hazardous driving conditions on local freeways. San Diego Union-Tribune, 5 Nov. 2022 The National Weather Service was also watching the tropics and said that hazardous boating conditions will be possible along the eastern Florida coast over the weekend. Leigh Morgan, al, 4 Nov. 2022 Reno also faced poor air quality that week as smoke from the Mosquito Fire — California’s largest fire of 2022 — created unhealthy to hazardous conditions. Thao Nguyen, USA TODAY, 3 Nov. 2022 Meanwhile, reports of sloppy practices, hazardous conditions and inadequate oversight reverberated across China’s laboratories, according to documents unearthed by Reid and reviewed by Vanity Fair and ProPublica. Katherine Eban, ProPublica, 28 Oct. 2022 See More

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

Word History


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

Dictionary Entries Near hazardous

Cite this Entry

“Hazardous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hazardous. Accessed 28 Nov. 2022.

Kids Definition



haz·​ard·​ous ˈhaz-ərd-əs How to pronounce hazardous (audio)
hazardously adverb
hazardousness noun

Legal Definition



: creating a hazard : involving or exposing one to risk (as of loss or harm)
a hazardous occupation
a hazardous substance
hazardously adverb

More from Merriam-Webster on hazardous

Last Updated: - Updated example sentences
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