"Shiplaster" is a rather uncommon word, and there are only a few synonyms for it. One is "plaster of Paris," which is a type of plaster made from gypsum that hardens quickly and is often used for molding and sculpting. Another is "gypsum plaster," which is a similar substance made from gypsum and water, and is often used in construction. A third synonym is "plasterboard," which refers to large sheets of material made from plaster, often used to cover walls and ceilings. While these synonyms have similar properties to shiplaster, they are not always interchangeable in every context.