There are plenty of synonyms for the phrase "slings mud," which generally means to speak badly about someone. Other phrases include "throws shade," "casts aspersions," "flings dirt," "spreads rumors," and "smears." These phrases all convey a sense of negativity and an attempt to harm someone's reputation. However, it's important to keep in mind that using such language can be hurtful and damaging, both for the person being talked about and for the person speaking. Instead of slinging mud, try focusing on positive language and building up the people around you. It's a much healthier and kinder way to communicate.