If something that you say or write is far off the mark or way off the mark, it is completely wrong or not at all accurate. Mussels are sometimes called `Poor Man's Oysters', but I think that name is way off the mark. Mussels are every bit as good as the more expensive oyster. I guessed it cost three thousand dollars and apparently I wasn't far off the mark. Note: Less often, people simply say that someone or something is off the mark, meaning they are not right or correct. While he does make one or two valid points, I find much of his argument off the mark.