When we talk about being "behind the curve", it refers to being out of touch or falling behind in a particular area or field. However, there are several other expressions that can effectively convey the same idea. One possible synonym is "lagging behind", which implies a slower progress compared to others. Another term is "outdated", which indicates being passé or no longer relevant. Similarly, "behind the times" conveys a lack of awareness or familiarity with current trends or advancements. Additionally, "old-fashioned" suggests ideas or actions that are no longer considered modern or up-to-date. Ultimately, all these synonyms give us an understanding of being behind in our knowledge, skills, or understanding of a subject.