Being a snitch is defined as informing or divulging information to someone in authority. However, if you prefer not to use the slang term 'snitch,' there are other words you can use instead. You can say that someone is reporting, tattling, ratting, or grassing up. You could also say that they are informing, leaking, exposing the truth, or revealing secrets. When it comes to talking about a person who is known for snitching, you can describe them as a tell-tale, squealer, stool pigeon, or rat. Overall, there are plenty of synonyms for the phrase 'be a snitch', so choose the one that fits best within the context and audience you are speaking to.