- The definition of an octagon is an eight-sided, eight-angled figure.
An example of an octagon is the shape of a stop sign in the US.
This stop sign is an octagon.
Origin of octagonClassical Latin octagonum ; from Classical Greek oktagōnos, eight-cornered: see octa- and amp; -gon
Origin of octagonLatin octagōnon, from Greek oktagōnon, from neuter of oktagōnos, octagonal : okta-, octo- + -gōnos, angled; see –gon.
First attested in 1656, from Latin octagonos, from Ancient Greek οκτάγωνος (oktágōnos, “eight-angled”), from ὀκτώ (octō, “eight”) + γωνία (gōnía, “angle”). The adjective octagonal was first mentioned from 1571.