On a collision course is a common phrase used to describe two or more entities heading towards each other with potential for conflict or disaster. However, there are several other phrases or synonyms that can be used to describe the same situation. Words like "on a collision path," "on a collision trajectory," or "heading towards a collision" can all be used interchangeably with "on a collision course." Other synonyms include "on a crash course," "destined to collide," "approaching a collision," and "headed for a collision." The use of synonyms can help provide variety and make writing more interesting while still conveying the same message.