The two-letter combination of "O-M" doesn't appear to have too many synonyms in the English language. However, the word "om" itself is often used as a synonym for "aum" or "ohm", a sacred sound and spiritual icon in Hinduism, Buddhism, and Jainism. Additionally, "om" can also be used as a synonym for "meditation" or "mindfulness", as it's often used as a mantra to aid in concentration and relaxation. When it comes to "O-M" specifically, there aren't any commonly accepted synonyms that come to mind. However, it's possible that some creative writers or poets could come up with alternative terms or phrases to substitute for this unusual combination of letters.