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

Stone continued working for the California EPA, in environmental crimes investigations for the Department of Toxic Substances Control, looking into large companies illegally disposing of hazardous waste. — Sacbee.com, 21 Sep. 2026

The city of Malibu is reminding the public of the hazardous conditions at Point Dume State Beach caused by ongoing severe coastal erosion. — Chelsea Hylton, CBS News, 20 Sep. 2026

These include dynamic proton radiography, materials science, neutron scattering, and nuclear physics, all operating at a facility authorized to use hazardous materials and handle classified data. — Rupendra Brahambhatt, Interesting Engineering, 19 Sep. 2026

In regards to what is happening on the streets of NYC — Kaporos — thousands of young Cornish chickens are kept in the streets in crates, in hazardous and dangerous conditions. — Voice Of The People, New York Daily News, 19 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