1
: not able to be trusted
a treacherous ally/enemy
: showing that someone cannot be trusted
a treacherous act of betrayal
treacherous misdeeds
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.
Cite this Entry
“Treacherous.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/treacherous. Accessed 22 Jun. 2026.
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