hazardous

1 of 2

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

hazardousness

2 of 2

noun

haz·​ard·​ous·​ness

plural -es

: the quality or state of being hazardous

deterred by the hazardousness of the enterprise

Synonyms of hazardous

Adjective

• 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

Adjective

It was a hazardous voyage.

These are hazardous chemicals that can cause death if inhaled.

Recent Examples on the Web

Adjective

Fires are often started illegally by plantation owners or traditional farmers to clear land for planting and those burns periodically blanket parts of Southeast Asia in hazardous haze, authorities said. — ABC News, 11 Aug. 2026

Severe fog or other hazardous weather can still stop an autonomous trip. — Kurt Knutsson, FOXNews.com, 10 Aug. 2026

Crews are still monitoring for hot spots and removing hazardous materials. — Jonathan Vigliotti, CBS News, 10 Aug. 2026

Marylanders are no stranger to environmental injustice; communities of color and low-income areas are disproportionately impacted by proximity to hazardous facilities. — Adrianne Fantasia, Baltimore Sun, 9 Aug. 2026

Word History

Etymology

Adjective

see hazard entry 1

First Known Use

Adjective

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