The phrase "onward course" refers to the direction or path that someone or something is taking. Synonyms for this phrase include "forward momentum," "continuing trajectory," "uninterrupted progress," "steady advancement," "persistent headway," and "unwavering direction." These synonyms all denote a sense of moving towards an intended goal, without deviating or being stopped. Other synonyms that convey a similar meaning to "onward course" include "forward path," "unchanging direction," "unswerving path," and "focused movement." Overall, these synonyms all suggest a determined and intentional movement towards a specific destination.