The phrase "in while" is typically used to refer to a short period of time or a brief moment. There are many synonyms that can be used to replace this phrase in different contexts. "For a moment" or "momentarily" can be used to indicate a brief duration of time. "Briefly" or "temporarily" can also be used to suggest a short-lived situation. Another option could be "in the meantime" or "meanwhile," which indicates that something is happening concurrently. Additionally, "momentary lapse" or "fleeting" could be used in a negative context to suggest a temporary mistake or lapse in judgment. Ultimately, there are many different phrases that can be used to replace the phrase "in while," depending on the intended meaning.