The term "the wrong side forty" refers to someone who is on the wrong side of their 40s, or middle-aged. If you're looking for synonyms to describe this stage of life, you might consider terms like "midlife," "middle-aged," or "past the half-century mark." Another way to describe this stage might be to use more positive language, such as "in the prime of life" or "experiencing life's second act." Alternatively, you could use more humorous language, such as "halfway to the century mark" or "nearing the big 5-0." Whatever terminology you choose, the important thing is to recognize and celebrate the wisdom and experience that comes with age.