ˌhigh-ˈrisk adjective [only before noun]
involving a risk of death, injury, failure etc Antonym : low-risk:
high-risk investments
high-risk patients/groups etc
cancer screening for women over 55 and other high-risk groups

[TahlilGaran] Dictionary of Contemporary English ▲

dangerous likely to cause death or serious harm, or cause something bad to happen:
Snow and ice are making driving conditions very dangerous.
dangerous drugs
a dangerous criminal
risky if something is risky, something bad could easily happen or you could easily make a mistake:
Doctors said it was too risky to operate.
a risky situation
hazardous /ˈhæzədəs $ -zər-/ especially written dangerous – used especially about substances, jobs, and journeys:
hazardous waste
hazardous chemicals
hazardous occupations
The expedition was extremely hazardous.
unsafe dangerous because someone is very likely to be hurt – used especially about places or conditions:
The roads are unsafe for cyclists.
unsafe working conditions
treacherous /ˈtretʃərəs/ formal literary places or conditions that are treacherous are very dangerous for anyone who is walking, driving, climbing etc in them:
The snow turned to ice, making conditions treacherous for walkers.
the island’s treacherous coastline
With no lighting, the roads can be treacherous.
perilous /ˈperələs, ˈperɪləs/ literary a perilous journey, situation etc is very dangerous:
a perilous journey across the sea
high-risk [only before noun] a high-risk job, situation, or behaviour is likely to be dangerous:
Drug users need to know that sharing needles is high-risk behaviour.

[TahlilGaran] English Thesaurus ▲