Source : Free On-Line Dictionary of Computing

MacLisp
     
        A dialect of {Lisp} developed at {MIT} AI Lab in 1966, known
        for its efficiency and programming facilities.  Later used by
        {Project MAC}, {Mathlab} and {Macsyma}.  Ran on the {PDP-10}.
        Introduced the {LEXPR} (a function with variable {arity}),
        {macro}s, {array}s, and {CATCH/THROW}.  Was once one of two
        main branches of LISP (the other being {Interlisp}).  In 1981
        {Common LISP} was begun in an effort to combine the best
        features of both.
     
        ["MACLISP Reference Manual", D.A. Moon
        , TR Project MAC, MIT 1974].