Synonyms for Dangerous:

adj.

adventurous (adjective)
risky, venturous.
all (adjective)
unsafe.
bad (adjective)
ruinous.
dangerous (adjective)
hairy, hazardous, insecure, menacing, ominous, perilous, precarious, risky, threatening, treacherous, unsafe, Jeopardous.
harmful (adjective)
malignant, bad.
hazardous, troubling (adjective)
alarming, bad, breakneck, chancy, critical, deadly, delicate, exposed, fatal, hairy, hot, impending, impregnable, insecure, malignant, menacing, mortal, nasty, parlous, perilous, portentous, precarious, risky, serious, shaky, speculative, thorny, threatening, ticklish, touch-and-go, touchy, treacherous, ugly, unhealthy, unsafe, unstable, vulnerable, Jeopardous.
severe (adjective)
bad, severe.

n.

alarming, bad, delicate, disastrous, endangered, exposed, hairy, hot, portentous, rickety, rocky, ruinous, safe, shaky, slippery, speculative, sure, thorny, ticklish, touchy, uncertain, unhealthy, unprotected, unstable, unsteady, vulnerable, unsheltered. armed, beneficial, deadly, explosive, fatal, helpful, imminent, impending, impregnable, innocent, malignant, mortal, nasty, ugly. adventurous, safety. help. dangerous (noun)
breakneck, chanceful, chancy, critical, desperate, dicey, dodgy, grave, grievous, harmful, hazardous, insidious, kamikaxe, on the hook, parlous, perilous, precarious, risky, self-destructive, serious, severe, suicidal, touch-and-go, treacherous, unreliable, unsafe, venturesome, venturous.

v.

frightening (verb)
alarming.

Other synonyms:

deadly, disastrous, ruinous. delicate, nasty, speculative. adventurous, fatal, mortal. hot. eruptive
explosive.
Other relevant words:
adventurous, alarming, bad, breakneck, chanceful, chancy, critical, deadly, delicate, desperate, dicey, disastrous, dodgy, endangered, explosive, exposed, fatal, grave, grievous, hairy, harmful, hot, impending, impregnable, insidious, kamikaxe, malignant, mortal, nasty, on the hook, parlous, portentous, rickety, ruinous, safe, self-destructive, serious, severe, shaky, slippery, speculative, suicidal, thorny, ticklish, touch-and-go, touchy, ugly, uncertain, unhealthy, unprotected, unreliable, unstable, unsteady, venturesome, venturous, vulnerable.

Usage examples for dangerous

  1. Miss Newton is too dangerous a character to leave at large. – The Lost Despatch by Natalie Sumner Lincoln
  2. He is a friend of yours, by- the- way; but he is not dangerous like Cartoner. – The Vultures by Henry Seton Merriman
  3. The question was a dangerous one to answer. – The Frozen Deep by Wilkie Collins