From The Free On-line Dictionary of Computing (30 December 2018) :
Emacs Lisp
A dialect of Lisp used to implement the higher
layers of the Free Software Foundation's editor, GNU
Emacs.++Sometimes+abbreviated+to+"{elisp">Emacs. Sometimes abbreviated to "{elisp". An enormous
number of Emacs Lisp packages have been written including
modes for editing many programming languages and interfaces to
many Unix programs.