tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans; "Punic faith"; "the perfidious Judas"; "the fiercest and most treacherous of foes"; "treacherous intrigues"
disapproval If you describe someone as treacherous, you mean that they are likely to betray you and cannot be trusted. He publicly left the party and denounced its treacherous leaders
dangerously unstable and unpredictable; "treacherous winding roads"; "an unreliable trestle
Like a traitor; involving treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust; faithless
If you say that something is treacherous, you mean that it is very dangerous and unpredictable. The current of the river is fast flowing and treacherous
dangerously unstable and unpredictable; "treacherous winding roads"; "an unreliable trestle"