septagon,a.|ˈsɛptəgən| [ad. late L. septagōnus, hybrid f. L. septem seven + Gr. -γωνος -angled, -gon.] Heptagonal. 1756T. Amory Buncle (1770) I. 215 Making it [basalt] into pentagon, hexagon, and septagon columns.1896Blackw. Mag. Apr. 597 The rock itself..cut into septagon shape.