An overnight case is typically a small, portable bag used to carry the essential items a person needs for an overnight trip. However, there are many synonyms you can use for this term, depending on your preference or the region you're in. Some people may call it a "duffel bag," "weekend bag," or a "carry-on bag." Others may refer to it as a "travel bag," "small suitcase," or simply an "overnight bag." More informal synonyms include a "grab bag," "go-bag," or "weekender." Regardless of the term used, the main purpose of it is to make travelling easier and more convenient.