[munificent]

> no other language has co-opted yet.

Check out Dylan, Julia, and my old hobby language Magpie[1].

[1]: http://magpie-lang.org/multimethods.html

[lisper]

I guess I should have said: no other mainstream language.

[PuercoPop]

Julia has generic function but they are not defined in Julia itself nor is dispatch mechanism can be extended in Julia itself. CLOS is all about meta-circular semantics so I wouldn't include Julia in there (at least not fully)