Learner's definition of TREACHEROUS
[more treacherous; most treacherous]
1 : not able to be trusted : showing that someone cannot be trusted 2 : very dangerous and difficult to deal with
sailing through treacherous waters
They were not prepared to hike over such treacherous terrain.
The snow made their hike all the more treacherous.
Discussions about money can lead couples into treacherous territory.