The phrase "on one game" refers to being focused and dedicated on a particular task or endeavor. There are several synonyms that can be used to express the same meaning, including "on top of one's game," "in the zone," "dialed in," "on fire," "locked in," and "in the groove." These expressions all convey a sense of being fully engaged and completely focused on a task or activity. Whether in sports, business, or any other area of life, staying "on one game" is often the key to success and achieving one's goals. Using these synonyms can help to convey a sense of confidence and determination in one's pursuits.