WordReference Random House Unabridged Dictionary of American English © 2026
non•a•gon
(non′ə gon′),USA pronunciation n.
non•ag•o•nal
(non ag′ə nl),USA pronunciation adj.
- Mathematicsa polygon having nine angles and nine sides. Also called enneagon.
- Latin nōn(us) ninth + -a- (extracted from pentagon, hexagon, etc.) + -gon
- 1680–90;
'nonagonal' also found in these entries (note: many are not synonyms or translations):