Homoiconic

Instead, the homoiconic paradigm draws from the mathematics of computability theory. […] In the case of a homoiconic programming language, the program processes itself, performing mechanical reductions on the application until there is nothing left except the answer.

Clojure and other languages from the Lisp family are homoiconic. In a homoiconic language, the source code of a program is represented as a plain data structure.