Как по Английски будет восьмиугольный

noun

A plane figure with eight straight sides and eight angles.

Примеры использования:

You may know about a pentagon, a hexagon, or an octagon.

adjective

Having the shape or cross section of an octagon; eight-sided.

Примеры использования:

An octagonal tower

adjective

Having eight angles.

Примеры использования:

The radar consisted of a large square transmitter array placed alongside an octangular receiving ar…

adjective

Designating or relating to a spiral arrangement of leaves in which there are eight leaves in each turn of the spiral about the stem, and thus eight vertical rows of leaves in the phyllotaxis.