pentagonal

adjective

pen·​tag·​o·​nal pen-ˈta-gə-nᵊl 

1

: having five sides and five angles

2

: having a pentagon as a cross section or as a base

a pentagonal pyramid

pentagonally

pen-ˈta-gə-nᵊl-ē 

adverb

Examples of pentagonal in a Sentence

Recent Examples on the Web

The asymmetric positioning of two proteins inside a pentagonal ring allows a proton from outside the cell to weakly bond to one of them. —Quanta Magazine, 20 Apr. 2026

Crafted with extraordinary precision, the piece features the traditional hexagonal and pentagonal panels of a soccer ball that come together to create a sphere. —Rachel Cormack, Robb Report, 22 Jan. 2026

For example, Palazzo Farnese in Caprarola is a stunning pentagonal palace with beautiful artworks by Renaissance and Mannerist painters. —Travel + Leisure Editors, Travel + Leisure, 28 Nov. 2025

The tiles form pentagonal arrangements, yet pentagons can’t fit snugly side by side to tile the plane. —Patchen Barss, Wired News, 5 Oct. 2025

Word History

First Known Use

1571, in the meaning defined at sense 1

Rhymes for pentagonal

• antiphonal
• embryonal
• faunal
• inconel

Kids Definition

pentagonal

adjective

pen·​tag·​o·​nal pen-ˈtag-ən-ᵊl 

1

: having five sides and five angles

2

: having a pentagon as a cross section or as a base

a pentagonal pyramid