On cue refers to something that happens at the right moment or at the appropriate time. There are several synonyms that can be used to replace the phrase "on cue". One of these is "right on time" which means something occurs at the scheduled time. Another synonym is "timely" which means happening at the appropriate moment. "Punctual" is also a synonym for on cue. It means something is happening at the exact specified time. "In sync" can also replace the phrase, referring to something happening in perfect coordination. Lastly, "prompt" can be used when referring to something happening quickly or without delay. These synonyms can be used to explain an event, an action or someone's response occurring at the perfect moment.