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English definition of “octagon”

octagon

noun [C]  /ˈɑk·təˌɡɑn/ us  
geometry a flat shape with eight straight sides and eight angles
octagonal
adjective [not gradable]  /ɑkˈtæɡ·ə·nəl/ us  
(Definition of octagon from the Cambridge Academic Content Dictionary © Cambridge University Press)
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