define-syntax

(define-syntax keyword (syntax-rules ...))

Binds keyword to a macro: a use (keyword ...) is replaced by the expansion its transformer answers before the program runs. Allowed at the top level and at the head of a body; a macro may expand into definitions. The macro is visible from its definition to the end of the file (or the body); a (load ...)ed file neither sees nor exports it. Only syntax-rules transformers are accepted. Macros are hygienic: a variable the template binds captures no name the use wrote, and a name the template uses freely means what it meant where the macro was defined.