So far ... the current definitions just prove that popular reference materials are not up to date ...
4 sided dice seem to have been the oldest manufactured dice 
8 sided dice have been manufactured since 1881 
12 sided dice have been around since ancient times 
20 sided dice have been around since ancient times as well 
An
unmounted solid object
with indicia (pips ... spots ... dots, numbers, letters, symbols, pictures etc)
on the extension member facets (faces or sides), edges or vertices
that is cast, rolled, spun or otherwise agitated
with the purpose of producing a
random indication of an indicia
