The name you want for "in the language" is EDSL: Embedded DSL. DSL is quite often used for library-level constructs but really, any concrete syntax (e.g. graphv

The name you want for "in the language" is EDSL: Embedded DSL. DSL is quite often used for library-level constructs but really, any concrete syntax (e.g. graphviz's dot format) is a DSL.