What is hit me up?

"Hit me up" is a colloquial phrase used primarily in informal conversations, particularly among younger people. It essentially means "contact me" or "get in touch with me." It's often abbreviated to "HMU." People use it to indicate that they are open to being contacted or to invite others to start a conversation or make plans. It's common in text messages and social media interactions. The phrase has become increasingly popular with the rise of digital communication, where brevity and informality are common.