The phrase "being behind" generally indicates a lag or delay in progress or timelines. Some synonyms to describe this may include shortfall, tardiness, lagging, falling short, or running behind. Alternatively, one could use phrases such as playing catch-up, having a backlog, or being in arrears to convey similar meanings. The context in which the phrase is used may also suggest other appropriate synonyms or phrases, such as being in the red financially, having unfinished work, or being behind schedule. Understanding the nuances of language can help convey a more precise message and minimize misinterpretation or confusion.