To start off with a broad statement, reality can be defined objectively or subjectively. This is personally perhaps one of the worst possible routes of defining such a term, yet it occurs all the time. We hear individuals say "well that's your reality" or "take a peek into my reality" or even a personal "favorite", "you are just outside of my reality" perhaps even outside of "their world"...
With all of the above statements, we see a requirement of subjectivity, opinion in comparison to objectivity, fact. The fact of the matter is, regardless of stance, we all are typing these words on philosophy stack exchange within the cosmos. Sure, we could argue different universes, yet such arguments are fiction based and rarely do anything for the foundation of logic other than disrupt it and furthermore make definitions themselves fuzzy... that is until we agree to put our intelligence aside and accept any and all definitions for any and all terms.
Despite all of this, you can find definitions of reality in textbooks and online that attempt at the least to define objectively. The problem with this still erupts as the words themselves are still not defined consistently amongst all of the sources available. Thus, my go to is defined as follows:
Reality: The world or state of things as they actually exist, as opposed to an idealistic or notional idea of them.
This seems to me to be the most concise definition that allows for a debunking of "personal realities". This can be done via understanding idealistic and even ideals themselves. Comparing and contrasting, in turn choosing a "favorite", hint, idealistic things rarely line up principally with ideals, at least via the roots of the words. We then compare and contrast notional things or notions themselves, another hint, notions are irrelevant. They undermine ideals and even principles, in turn paving the way for idealistic "realities".
If this can be done properly, we may just see the path to gathering different philosophies and ideals in the effort of objectively knowing reality to a cosmic scale... perhaps.
Regardless, reality is something that requires an objective definition to even be relevant, as its relevance is used as a quantification to define the "active" state of existence. Within the cosmos, we see the universe or universes, then the galaxy or galaxies, even star systems, stars, planets, suns and moons. That is the reality of our existence, to argue this as nothing but "personal perspective" seems to be nothing but incompetent. With such an acknowledgment, I'd argue we at the least have a foundation to understand reality as objective and perhaps even fixed, as in not allowing a changing definition, rather, the definition itself defining perpetual changes that occur via existence.