There are various synonyms that one can use for the term "stay behind". Some common ones include "remain", "linger", "wait", "stay put", "hang back", "hold back", "stay back", "trail behind", "lag behind", and "tarry". Depending on the context, some of these synonyms may be more appropriate than others. For example, "remain" may be used to indicate that someone is staying in a particular place, while "tarry" may suggest a delay in departing from a place. Ultimately, the choice of synonym will depend on the specific situation and the intended meaning that the writer or speaker wants to convey.