The phrase "are behind" can be replaced by a variety of synonyms, depending on the context. For instance, "lagging," "trailing," or "falling behind" can be used to describe someone's relative position when compared to their peers. Similarly, "delayed," "late," or "not up to speed" are appropriate alternatives when referring to a project or task that's behind schedule. In a more sinister sense, "underhanded," "sneaky," or "devious" might be used to describe someone's motives when it appears they're knowingly trying to keep something hidden or obscure. Regardless of the meaning, the right synonym can add punch to language and help make communication more clear.