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

In use, the explosive charge first breaks open the containers or bunkers holding the hazardous materials. —Bojan Stojkovski, Interesting Engineering, 8 Mar. 2026

Critics such as the Friends of the Mississippi River have said Alternative 4’s half-measures would fail to address the hazardous waste in the middle of the pile, focusing instead on removing surface debris along its southern edges while installing erosion controls. —Frederick Melo, Twin Cities, 8 Mar. 2026

Black smoke billowed over the Iranian capital, with officials there warning of the hazardous health effects for residents. —Kevin Rector, Los Angeles Times, 8 Mar. 2026

The franchise, named in legal documents as the Athletics Investment Group, sought in January to end an exemption that for years has allowed Radius’ facility in West Oakland to produce allegedly hazardous waste without meaningful regulation. —Shomik Mukherjee, Mercury News, 8 Mar. 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