I have only a limited knowledge of Lisp (trying to learn a bit in my free time) but as far as I understand Lisp macros allow to introduce new language constructs and syntax by describing them in Lisp itself. This means that a new construct can be added as a library, without changing the Lisp compiler / interpreter.
This approach is very different from that of other programming languages. E.g., if I wanted to extend Pascal with a new kind of loop or some particular idiom I would have to extend the syntax and semantics of the language and then implement that new feature in the compiler.
Are there other programming languages outside the Lisp family (i.e. apart from Common Lisp, Scheme, Clojure (?), Racket (?), etc) that offer a similar possibility to extend the language within the language itself?
Please, avoid extended discussion and be specific in your answers. Instead of a long list of programming languages that can be extended in some way or another, I would like to understand from a conceptual point of view what is specific to Lisp macros as an extension mechanism, and which non-Lisp programming languages offer some concept that is close to them.