The phrase "a backstabber" is correct and usable in written English.
It is typically used to describe someone who betrays or undermines another person, often in a deceitful manner.
Example: "I thought we were friends, but I found out he was a backstabber, spreading rumors about me behind my back."
Alternatives: "traitor" or "double-crosser".
Don't get stuck with a backstabber.
Fans had been waiting for months to unleash their anger, to call James a traitor and a backstabber and a fraud at close range.
He's already turned up in The Australian with his private campaign submission – virtually at least – characterising her as a backstabber driven by ambition.
Rattled by Kejriwal's popularity, Modi has taken to the campaign trail, portraying his rival as a backstabber who betrayed voters last time round by quitting so early.
One more little problem: Lutz is not a backstabber, and this is a business in which backstabbing is fine art.
Chamberlain was livid with Russell and saw him as a backstabber.
Some poor behaviors, such as being persistently late, sloppy, or selfish are a sign of a thoughtless person, not necessarily a scheming backstabber.
MR: Cool, getting back to "Mean To Me"... BK: "Mean To Me" was written when I was on tour in Australia and I just got off of this US run, working with somebody that just turned out to be a total backstabber and just kind of like a really evil person who was pitting people against each other and talking s**t.
According to the naysayers, the Facebook CEO was making the donation to counteract the negative depiction of him in The Social Network as, in the words of the New York Post, "a conniving backstabber who may have stolen the idea for his social networking site".
If she likes you, but you are considered a jerk, backstabber, player or anything else negative she will more than likely keep her feelings to herself.
Chloe (Krysten Ritter) is a deadpan, empathy-free vampiric backstabber with a history of terrorising roommates to the point where they flee and she keeps their deposits.
