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

Crystal Lake became filled with hazardous sediment and waste by 2024, according to an Aark Wildlife Rehabilitation and Education Center blog post. — Ingrid Vasquez, PEOPLE, 29 Sep. 2026

Energy experts previously dismissed these natural geological anomalies as hazardous and rare. — Mrigakshi Dixit, Interesting Engineering, 29 Sep. 2026

Ralph Armstrong, who spent nearly 20 years working as a utility worker and now serves as senior assistant business manager for IBEW Local 1245, said those incidents have added stress to an already hazardous job. — Darrielle Fair, CBS News, 29 Sep. 2026

During the summer, the sheriff’s bomb squad and the naval explosive ordnance disposal unit also responded to the beach to pick up a much more hazardous item, a Super Bazooka round. — Karen Garcia, Los Angeles Times, 29 Sep. 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