The phrase "figure of the earth" is often used to refer to the shape of the planet. However, there are several synonyms that can be used to describe this concept. One common term is "geoid," which refers to the irregular shape of the Earth's surface due to variations in gravity and other factors. Another term is "ellipsoid," which refers to the shape of the Earth as an oblate spheroid or flattened sphere. "Terrestrial reference frame" is another synonym often used in geodesy to describe the Earth's physical shape. All of these terms describe the same basic concept, but each emphasizes different aspects of the Earth's shape and structure.