That's a custom operator definition. Operator overloading is when the same operator can be used on different types (for example, if `+` worked on both floats and ints, instead of explicitly having to reach for the correct `+` like you do in OCaml).
Yeah, I guess you can get a limited sort of operator overloading by building it out of row polymorphism. That doesn't solve the most common use-case of operator overloading, though, which is allowing the same operators to work on floats and ints, because it only works on objects.