When someone talks about you behind your back, it can be very hurtful. We all want to feel like we are respected and appreciated, so it can be difficult to deal with when we feel like somebody is betraying our trust. Fortunately, there are many synonyms for the phrase "behind one's back" that can be used to describe this kind of behavior. Some of these include "in secret", "without someone's knowledge", "surreptitiously", and "covertly". No matter what word you use to describe this kind of behavior, it's important to remember that it is never okay to talk about someone behind their back. Always treat others with kindness and respect, even when they're not around.