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

Occupational Safety and Health Administration investigators also found the company did not adequately train its employees to recognize fall hazards and did not use a hazard communication program for employees using hazardous chemicals, the news release said. —Angie Dimichele, Sun Sentinel, 25 Apr. 2026

At the facility, officials found several bodies in hazardous conditions inside the building that was later condemned and demolished by federal environmental regulators as a toxic waste site. —Eduardo Cuevas, USA Today, 25 Apr. 2026

The warehouse includes more than 100,000 feet of containerized hazardous materials storage for chemicals used in semiconductor production, according to the lawsuit. —Cara Tabachnick, CBS News, 25 Apr. 2026

The work is being guided by state environmental regulations that govern the handling of asbestos and other hazardous materials that can become airborne, according to Jeff Auker, the city’s director of development services. —Kenneth R. Gosselin, Hartford Courant, 24 Apr. 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