Round angle is a term that is commonly used in geometry to describe an angle that measures 180 degrees. There are several synonyms for this term, including straight angle, flat angle, and line angle. A straight angle is an angle that measures exactly 180 degrees and appears as a straight line. A flat angle is a term used to describe an angle that has the appearance of a flat surface. A line angle is a term used to describe an angle that is formed by two intersecting lines and measures 180 degrees. These synonyms help to describe the same concept in different ways, making it easier for individuals to understand and apply in their studies or work.