The term "trundle-bed" refers to a type of bed that has a smaller bed underneath it that can be pulled out. Some synonyms for "trundle-bed" include roll-out bed, wheeled bed, and under-bed sleeper. Additionally, some people may refer to this type of bed as a daybed with a trundle or a pop-up trundle bed. No matter the specific name used, trundle-beds are popular choices for guest rooms and children's bedrooms as they allow for additional sleeping space without taking up much floor space when not in use.