perilous

adjective

per·​il·​ous ˈper-ə-ləs 

ˈpe-rə-

: full of or involving peril

a perilous journey

perilously adverb

perilousness noun

Synonyms of perilous

• dangerous
• hazardous
• risky
• serious

Choose the Right Synonym for perilous

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 perilous in a Sentence

a perilous journey across the mountains

a perilous journey through hostile territory

Recent Examples on the Web

Moreover, investing in a single stock without thorough analysis can be perilous. —Trefis Team, Forbes.com, 23 Jan. 2026

Both North Texas and neighboring Oklahoma are expected to be hit hard by the winter storm, with both anticipating perilous roadway conditions and power outages from a combination of freezing rain, ice, sleet, snow and strong wind gusts. —Lauren Caruba, Dallas Morning News, 23 Jan. 2026

Despite the influx of capital and computing power, the transition from algorithmic prediction to clinical cure remains perilous. —Nick Lichtenberg, Fortune, 23 Jan. 2026

Local officials have grown increasingly wary of unprepared and inexperienced hikers setting out on some of the toughest peaks during perilous conditions. —Grace Toohey, Los Angeles Times, 22 Jan. 2026

Word History

Etymology

Middle English perilous, perelous, borrowed from Anglo-French perilleus, perillous, going back to Latin perīculōsus, from perīculum "test, risk, peril entry 1" + -ōsus -ous

First Known Use

14th century, in the meaning defined above

Rhymes for perilous

• carolus
• garrulous
• querulous
• puberulous

Kids Definition

perilous

adjective

per·​il·​ous ˈper-ə-ləs 

: full of or involving peril

perilously adverb

perilousness noun