From The Free On-line Dictionary of Computing (30 December 2018) :
Emacs LispA 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.