What is a word that means "someone who pretends to be your friend but is actually your enemy?"
After you discover how he has turned on you, you might call him:
- a false friend [not to be confused with the linguistic term of the same name]:
not faithful or loyal : treacherous <a false friend> (m-w.com "false", def. 4a) - a traitor:
one who betrays another's trust or is false to an obligation or duty (m-w.com def 1) - a backstabber:
[one who engages in] betrayal (as by a verbal attack against one not present) especially by a false friend (m-w.com def. 1) - a double-crosser:
to cheat or deceive (someone) especially by doing something that is different from what you said you would do (m-w.com def. 1) - a two-timer:
1: a double-crosser
2: one who betrays (a spouse or lover) by secret lovemaking with another (m-w.com) disloyal:
failing to support or be true to someone or something : not loyal or faithful to your friends, family, country, etc. (m-w.com)perfidious:
not able to be trusted : showing that someone cannot be trusted : characterized by perfidy (the act of betraying someone or something : the state of not being loyal) (m-w.com)
There are lots of possible answers here.
This is quite a common social dynamic, so a lot of words have been discovered to be relevant.
Frenemy is a portmanteau that exactly describes this situation.
frenemy noun - one who pretends to be a friend but is actually an enemy [Merriam-Webster]
Personally though, I think this a rather cringey word, I'd much sooner use some of the other suggestions.