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

Mathieu Lewis-Rolland / Getty Images The tank was designed to hold 900,000 gallons of a hazardous chemical known as white liquor, a chemical brew that contains sodium hydroxide, sodium sulfide and disodium carbonate and is used in the paper-pulping process, officials have said. —Marlene Lenthang, NBC news, 31 May 2026

Avoid burning plastics, hazardous materials or household trash. —Nick Lentz, CBS News, 31 May 2026

Remain out of the water to avoid hazardous surf and NEVER turn your back on the ocean. —Ca Weather Bot, Sacbee.com, 31 May 2026

In 2021, the EPA accused the company of failing to perform daily checks of a chemical tank, not containing MMA, for 25 days, failing to properly label hazardous material and having excessive levels of volatile organic compounds — 20 times the allowable limit — near a vent. —Jason Henry, Oc Register, 30 May 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