- treacherous, unreliable - dangerously unstable and unpredictable; "treacherous winding roads"; "an unreliable trestle"
Antonym: safe (indirect, via dangerous)
- punic, perfidious, treacherous - 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"
Antonym: faithful (indirect, via unfaithful)