The phrase "coming on to" usually refers to making flirtatious or sexual advances towards someone. There are several synonyms that can be used to convey a similar meaning. "Flirting with" is a common phrase that suggests making suggestive gestures or remarks to another person. "Seducing" implies the intention to lure or entice someone into a sexual situation. "Hitting on" or "making a pass at" can indicate a direct and aggressive approach. "Romancing" is less specific but still suggests an attempt to woo or charm someone. Ultimately, the choice of synonym will depend on the context and level of intimacy or aggression desired.