The general term is "pyramid". A nonagonal pyramid would be one where the base has nine sides; if you're referring to the sides of the solid object, it would be an octagonal pyramid (8 "sides" plus the base = nine sides total).
A nonagon based pyramid.
Hexagon shaped pyramid
a nonagon is the name given to a nine sided polygon
well actually it is a prism. If you mean a 5 sided pyramid with the 6 side being the bottom it would be called a Pentagonal Pyramid
A pyramid
D9
Nonagon
Nonagon
Either a nonagon or an enneagon. Whichever floats your boat.
it is called a nonagon.
A nine sided shape or polygon is called a nonagon.