The term "meta-language" shouldn't be used to identify a specific language; it's a general term for a language that describes or manipulates another language(s)

The term "meta-language" shouldn't be used to identify a specific language; it's a general term for a language that describes or manipulates another language(s). For instance, the rules language for XTRAN, our Expert System, is a meta-language, and we call it "meta-code", because it manipulates many different computer languages (including itself!), as well as data and text. A well-known ML example is Backus-Naur Form (BNF), which is a meta-language for specifying well-formed statements in a language. We use BNF to drive XTRAN's parsing engine, which executes the BNF at parse time.