Hit up is a colloquialism that means to visit or contact someone, usually with the intention of socializing or asking for a favor. There are several synonyms that can be used instead of hit up depending on the context. Some popular options include contact, reach out to, connect with, catch up with, drop in on, visit, swing by, and drop a line to. These words can be used interchangeably based on the formality of the situation and the tone you want to convey. Regardless of the synonym you choose, the general meaning of hit up remains the same - making contact with someone for a friendly interaction.