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

Interestingly, though, pentagonal arrangements of atoms can fill space in almost-but-never-quite-repeating patterns with fivefold symmetry, forming materials called quasicrystals. — Natalie Wolchover, Quanta Magazine, 10 Aug. 2026

The quadrilateral, pentagonal and hexagonal cases all obey this formula, but no larger shapes have been confirmed. — Jack Murtagh, Scientific American, 10 Aug. 2026

The theater is made up of 316 individual hexagonal and pentagonal shapes in 16 different sizes. — Anthony D'alessandro, Deadline, 21 July 2026

These limbs are positioned according to a regular dodecahedral geometry, a structure defined by 12 pentagonal faces, producing a highly uniform distribution of both force and visual coverage. — Jijo Malayil, Interesting Engineering, 27 May 2026

Word History

First Known Use

1571, in the meaning defined at sense 1

Rhymes for pentagonal

• antiphonal
• 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