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

• 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

Fire crews sometimes allow lightning-strike fires to burn, and made the decision to do that on the Dragon Bravo Fire, intended to reduce hazardous fuels and vegetation along the North Rim of the Grand Canyon. —Hayleigh Evans, AZCentral.com, 15 July 2025

Map of damage: See how the Texas floods unfolded and why Camp Mystic was in a hazardous location The death toll has risen to 129 on Saturday, including more than three dozen children. —Kathryn Palmer, USA Today, 14 July 2025

The blaze, fueled by extreme heat, low humidity, and fierce winds, forced evacuations, led to a hazardous chlorine gas release, and resulted in the seasonal closure of the North Rim for visitors and park staff, Inciweb shows. —Hollie Silverman, MSNBC Newsweek, 13 July 2025

Instead of a crew of 10 spending months sanding and grinding around rivets, the laser burned off the paint and debris in only days, with a HEPA filter sucking up hazardous dust. —New Atlas, 12 July 2025

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