pentagonal

adjective

having five sides and five angles

Wiktionary

Pronunciation: /pɛnˈtæɡənəl/

adj

Etymology: Etymology tree English pentagon Proto-Indo-European *h₂el-der.? Proto-Italic *-ālis Latin -ālisbor. Old French -albor. ▲ Latin -ālis Old French -elbor. ▲ Latin -ālisbor. Middle English -al English -al English pentagonal From pentagon + -al.

Of, relating to, or shaped like a pentagon.
“If the base be a triangle, it is called a triangular prism; if a square, a square prism; if a pentagon, a pentagonal prism; and' if the base is any irregular figure, it is called an irregular prism : ...”
“Seed micromorphology:—Seed coat is laticostate. Epidermal cells are elliptical to irregularly pentagonal. Cell walls are thickened mostly at the corners, the boundaries are raised […]”

noun

Something having the shape of a pentagon.
“Speaking of protection, note that not only are the end pentagonals surrounded by a generous air space, but the entire instrument is insulated, […]”
“The pentagonals with the flowers and the leaves of the central calyx are gilded all over, as is the inner lip of the vessel.”