1. A plastic building material made by mixing lime, cement, sand, and water. Cement mortar is used to bind masonry blocks together or to plaster over masonry. 2. Any cement used for mortar of masonry walls. Masonry cements are generally more workable than normal Portland cement. They usually start with a Portland cement base and add hydrated lime, crushed limestone, diatomaceous earth or granulated slag to aid in spreading. Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis]