Three-cornered is a word used to describe an object or shape with three distinct corners or points. However, there are several synonyms that can be used to describe this geometric shape. One of the most common synonyms is triangular, which means "in the shape of a triangle." Another synonym is trifoliate, which means "having three leaves or leaflets." You can also use the term trilateral, which refers to a shape or object with three sides or edges. Other synonyms for three-cornered include trigonal, triangularly shaped, and tripartite. Using these synonyms can help to add variety and depth to your writing, making it more interesting and engaging for your readers.