Well, they are not functions and they are not macros. It seemed appropriate to overload the 'mixin' name, but it's not too late to find a better name.

Even if Beef supported class mixins, I would say "there's class mixins and method mixins". D does something similar with template mixins vs a mixin statement that compiles strings as code.

Try “Inline”?

To me, an "inlined" method already has a specific meaning -- it's a type of optimization that does not infer a semantic difference to a normal method.