Inventation

[Julian]

n, An invention that has not [yet] been [invented].
n, an invention that is still an [idea]

[Agnes]

From [invent] and invitation. Lacking a [formal] invitation, inventing your own; to [invite] ones self

[JCK 9500]

@agnes Love it! Thank you. I was having trouble finding a definition that fit the usage at a particular website: "Become a Member!
An Inventation to Join the FFAA"