An icosagon is a 20-sided polygon, but there are several other synonyms for this shape. One of the most common is "20-gon," which is simply short for "20-sided polygon." Another synonym is "vigintagon," which comes from the Latin word "viginti" meaning "twenty." Additionally, some people refer to an icosagon as a "regular 20-sided polygon" or a "convex 20-gon," emphasizing the straight edges and lack of concavity in this shape. Finally, if you're feeling especially poetic, you might refer to an icosagon as a "dodecakaidecagon," which is Greek for "twelve ten-sided figures." Regardless of the term you choose, an icosagon is an interesting and complex shape that's worth exploring in more depth.