Macro LAMBDA form.
Example:
(DEFMACRO X/Y-GUARD (X Y) (MLAMBDA (X Y) (AND (RATIONALP X) (RATIONALP Y) (NOT (EQUAL Y 0))))) = (DEFMACRO X/Y-GUARD (X Y) (LIST 'AND (LIST 'RATIONALP X) (LIST 'RATIONALP Y) (LIST (LIST 'NOT (LIST 'EQUAL Y 0))))) = (DEFMACRO X/Y-GUARD (X Y) `(AND (RATIONALP ,X) (RATIONALP ,Y) (NOT (EQUAL ,Y 0))))
MLAMBDA is a macro LAMBDA. MLAMBDA converts form to a lisp macro body, substituting all symbols except those that appear in the args with the quoted symbol.