An ancient Egyptian mud-brick tomb with a rectangular base and sloping sides and flat roof WordNet 3.0 & Open English WordNet

A mastaba, also mastabah, mastabat or pr-djt, is a type of ancient Egyptian tomb in the form of a flat-roofed, rectangular structure with inward sloping sides, constructed out of mudbricks. Wikipedia

Type of ancient Egyptian tomb Wikidata

A rectangular structure with a flat top and slightly sloping sides, built during Ancient Egyptian times above tombs that were situated on flat land. Mastabas were made of wood, mud bricks, stone, or a combination of these materials. Some are solid structures, while others can contain one or more rooms, sometimes decorated with paintings or inscriptions. Wiktionary

Rectangular structure with a flat top and slightly sloping sides. Wiktionary (translation)