A computer built totally on Lisp. Even its processor ran a form of Lisp.

This concept is also known as Lisp all the way down meaning there is Lisp at every level of the system.

Emacs as a LispMachine

Some people have started to refer to Emacs as a LispMachine. It is not strictly a LispMachine because, clearly, it is a software program and not a physical computer, but as that line starts to blur it seems like a useful epithet for Emacs because these days Emacs look more and more like an operating system.

Emacs as an OperatingSystem is, in fact, a common joke Emacs is a great operating system, it just doesn't have a good editor.