There is a plethora of synonyms for the phrase "riding off". These substitute terms can be used to convey the same meaning but in a different way. The most commonly used synonym is "galloping away," which refers to moving in a hurry in a particular direction. Another term that can be used in this context is "riding away," which means departing from a place or moving away from something. Other alternatives include "leaving on horseback," "heading out," or "riding forth." These synonyms add a different flavour to the sentence and can be used interchangeably based on the context.