Octagonal means having eight sides and eight angles. Some synonyms for the phrase "most octagonal" could be: the most eight-sided, the most polygonal with eight sides, the most angular with eight corners, or the most regular polygon with eight sides and angles. Other terms could include the most stop-sign shaped, the most eight-cornered, or the most octahedral, which is a term used in geometry to describe a shape with eight equally sized faces and angles. These synonyms help to provide a better understanding of the shape and emphasize the eight-sided nature of the object in question.