Illustration of heptagon
heptagon
noun
hep·ta·gon ˈhep-tə-ˌgän 
: a polygon of seven angles and seven sides
heptagonal
hep-ˈta-gə-nᵊl
adjective 
Example Sentences
Recent Examples on the Web At least show some imagination and go for a heptagon next time. 
Nate Davis, USA TODAY, 9 Sep. 2022 Nearby, the bug must make seven such turns, signifying a heptagon with an equal and opposite amount of negative curvature, the kind in a saddle. Quanta Magazine, 6 Jan. 2015
Nate Davis, USA TODAY, 9 Sep. 2022 Nearby, the bug must make seven such turns, signifying a heptagon with an equal and opposite amount of negative curvature, the kind in a saddle. Quanta Magazine, 6 Jan. 2015 Word History
Etymology
Greek heptagōnos heptagonal, from hepta + gōnia angle — more at -gon
First Known Use
1570, in the meaning defined above
Kids Definition
heptagon
noun
hep·ta·gon ˈhep-tə-ˌgän
: a closed geometric figure having seven angles and seven sides