hazardous

adjective

haz·​ard·​ous ˈha-zər-dəs 

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

• dangerous
• perilous
• risky
• serious
• unsafe

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

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

The American Chemistry Council, the chief trade group for plastics manufacturers, contends academic researchers haven’t proven the industry’s products are hazardous. —Michael Hawthorne, Chicago Tribune, 21 June 2026

Moore cautioned people with lung issues or smoke sensitivity to avoid outdoor activities, but said crews have mitigated the hazardous-materials portion of the blaze and are now focused on the biohazard portion posed by spoiled food. —Arkansas Online, 21 June 2026

Officials cautioned people with lung issues or smoke sensitivity to avoid outdoor activities, but said crews have mitigated hazardous materials at the site. —Hayley Smith, Los Angeles Times, 21 June 2026

Authorities said hazardous material risks have largely been mitigated, but the situation is now shifting toward potential biohazard issues as food inside the facility remains unrecovered. —Iris Salem, CBS News, 20 June 2026

Word History

Etymology

see hazard entry 1

First Known Use

1549, in the meaning defined at sense 1

Rhymes for hazardous

• nonhazardous

Kids Definition

hazardous

adjective

haz·​ard·​ous ˈhaz-ərd-əs 

: 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