"Semilunar" is a word that describes the shape of a crescent or a half-moon, and can be used as a synonym for "semi-tuberous." "Ellipsoid" is another synonym, which refers to anything that is shaped like an oval or an ellipsis. "Bulbous" is a word that describes something that is rounded or swollen, and can be used to indicate a plant or flower with a bub-shaped stem or bulbous roots. "Spheroid" refers to any object that is shaped like a sphere, and can be used to describe a semi-tuberous plant with a round or spherical shape. Finally, "ovate" is a term that refers to anything that is egg-shaped or oval, which could also be used as a synonym for "semi-tuberous".