Dictionary.com
Thesaurus.com
Synonyms

dangerous

American  
[deyn-jer-uhs, deynj-ruhs] / ˈdeɪn dʒər əs, ˈdeɪndʒ rəs /

adjective

  1. full of danger danger or risk; causing danger; danger; perilous; risky; hazardous; unsafe.

  2. able or likely to cause physical injury.

    a dangerous criminal.


dangerous British  
/ ˈdeɪndʒərəs /

adjective

  1. causing danger; perilous

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

dangerous Idioms  
  1. see little knowledge is a dangerous thing; live dangerously.


Other Word Forms

  • dangerously adverb
  • dangerousness noun
  • nondangerous adjective
  • nondangerously adverb
  • nondangerousness noun
  • quasi-dangerous adjective
  • quasi-dangerously adverb
  • semidangerous adjective
  • semidangerously adverb
  • semidangerousness noun
  • undangerous adjective
  • undangerously adverb

Etymology

Origin of dangerous

First recorded in 1175–1225; Middle English da(u)ngerous “domineering, fraught with danger,” from Old French dangereus “threatening, difficult,” equivalent to dangier ( danger ) + -eus -ous

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Starting in January 2025, Nokia’s sensors had picked up a series of increasingly powerful cyberattacks coming from devices that hadn’t previously been considered dangerous.

From The Wall Street Journal • Apr. 3, 2026

"It's suffocating," the 36-year-old coconut seller told AFP in Chiang Mai, a tourist destination among the areas affected by dangerous pollution levels this week.

From Barron's • Apr. 3, 2026

“President Trump promised to reinvest in America’s national security infrastructure, to make sure our Nation is safe in a dangerous world,” the document reads.

From Salon • Apr. 3, 2026

But UConn will return Sarah Strong and Blanca Quiñonez, South Carolina has Edwards back and Texas has another year of Madison Booker, and other up-and-coming squads like Michigan and USC will be dangerous.

From Los Angeles Times • Apr. 3, 2026

“The sphinxes will know we landed. It’s best not to keep them waiting. An impatient sphinx is a dangerous thing.”

From "Impossible Creatures" by Katherine Rundell