A trundle bed (or truckle bed) is a low, wheeled bed that is stored under a twin/single bed and can be rolled out for use by visitors or as just another bed.
A pop-up trundle bed can be raised to meet the height of the normal bed, effectively creating a wider sleeping surface when positioned side-by-side.
- ^ Cambridge Advanced Learner's Dictionary and Thesaurus. Cambridge University Press. Archived from the original on 2016-09-10. Retrieved 2016-08-03.