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 Department of Toxic Substances Control is tasked with enforcing laws and regulations governing hazardous waste and hazardous substances, according to the agency’s website. — Los Angeles Times, 6 Oct. 2026

The robots are expected to assist with hazardous-material response, blast investigations, prison searches and other tasks that could put human personnel at risk. — Jijo Malayil, Interesting Engineering, 5 Oct. 2026

Ensure heat is working so tenants don’t need space heaters, which can be particularly hazardous in buildings with older electrical systems. — Lillian Bonsignore, New York Daily News, 4 Oct. 2026

The action comes as Livingston locals raised concerns about the film’s impact on local business — and notably the city’s sole food bank — as well as improper notification about hazardous stunts. — Payton Turkeltaub, Variety, 4 Oct. 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