@Kaldrak As far as my understanding goes, a harem is where you make everyone fall for you whereas a reverse harem is when everyone has already fallen for you without you even doing anything, regardless of whether you like it or are even aware of it.
@GoggledAnon Curious. I've never seen the tag applied to any of the ones with a male MC surrounded by women who fawn all over him for no reason other than the author wants them to. I've only ever seen the tag applied to Female MC's. Regardless, even if your definition is correct, it's a distinction without a purpose, in my mind.