A plane figure with seven angles and seven straight sides; a heptagon. Also: a building or object of heptagonal form or cross-section. Now somewhat rare.
Having seven angles and seven straight sides; heptagonal.
Early 17th century; earliest use found in Aaron Rathborne (b. ?1572), land surveyor and author. From classical Latin septagōnus heptagonal (in texts on land surveying) from septem seven + ancient Greek -γωνος.