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

Protecting identities, networks, software and data remains essential, but what happens if AI makes the wrong decision, is manipulated, exceeds its authority or creates a hazardous physical intervention? — Gregory Shahnovsky, Forbes.com, 13 Oct. 2026

Technicians could operate tools in inaccessible areas, reducing the need to send personnel into hazardous environments. — Aamir Khollam, Interesting Engineering, 13 Oct. 2026

Both the driver and semi were taken to the Newton-Azrak Station in Murrieta, where hazardous response specialists extracted the liquid contents from the tank, which tested positive for meth, the release said. — Dean Fioresi, CBS News, 13 Oct. 2026

The facility has sign for consumer advisory for undercooked food, and the potentially hazardous items are marked, but the sign is lacking asterisks. — Arkansas Online, 12 Oct. 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