It's a relative thing. I think it can only be defined relative to some specified alternative, like inflation targeting. It doesn't mean anything otherwise.
There are n different things a central bank could target, where n is an extremely large number. (Strictly, n is infinite, since any combination of two members of n is also a member of n.) One of those n things is the exchange rate. I know what "fixed exchange rates" means: it means the central bank targets the exchange rate. That leaves n-1 other things the central bank could target. But each of those n-1 different things would have different implications for how the exchange rate would change over time in response to various shocks.