"Off the mark" is a common expression used to describe something that is inaccurate or incorrect. There are several synonyms that can be used to convey a similar meaning, including "off target," "wide of the mark," "missed the mark," "incorrect," "inaccurate," "wrong," "imprecise," "inexact," and "mistaken." Each of these words can help to express a different nuance of the concept of being "off the mark," from simply missing the intended target to being completely wrong in one's assessment or understanding. Using these synonyms can help to add variety to one's writing and communication, while still conveying the desired meaning.