I guess I should have said: no other mainstream language.
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)
Check out Dylan, Julia, and my old hobby language Magpie[1].
[1]: http://magpie-lang.org/multimethods.html