IPA: /ˌpɛntəˈɡɒnəli/
KK: /pɛntəˈgɑnəli/
In a shape or manner that has five sides and five angles.
The artist designed the building pentagonally to create a unique look.
Pentagonally → It is formed from "penta-" (from Greek "pente", meaning five) and "-gon" (from Greek "gonia", meaning angle) and "-ally" (meaning in a manner). The word describes something that is in the manner of five angles or sides, as in the shape of a pentagon.
Think of 'five' ('penta-') angles ('-gon') to remember that 'pentagonally' refers to something related to a five-sided figure.