It’s not a definition, it’s an implementation. A definition would be something like ”constrain a number to an interval defined by two other numbers”. That happens to be identical to sorting and picking the middle value. The only difference vs OP’s clamp is that it gives a consistent and predictable result for ”inverted” intervals where min > max, instead of arbitrarily deciding how to collapse the interval.

It is a definition. You've defined the behaviour when min>max and you've chosen a weird way to define it.