The websites of the internet are messing with the 'definition' but it had always (since man began writing) meant: Man/wife, family. Latin from the Catholic Church definition maintained it in the biblical sense such that the state simply adopting the term, not only messes up the term in the U.S. but the rest of the English-speaking world. Either the state or the church has to move to another term if the dictionary definition is obscured to something else. It would obviously have to because the strict sense is all Scripture gives. It is unfortunate that the state didn't think this all through to the logical problems and just bull-headed and steam-rolled. We are in a reckless age that doesn't 'need' to move quite that recklessly or fast. "Civil-union" would have been the better, causing a lot less problems. There may yet have been a few complaints, but the new term wouldn't have rankled like the SCOTUS hand-me-down inept hammer fest. I think they need a better check/balance because the Constitution didn't really envision 'inept' from all 9 justices. They are too pop culture and too easily swayed by media and entertainment themselves.
No person or group owns an idea or the term representing it. These are phenomena experienced and practiced collectively. And the idea of pair-bonding is no exception. It is not a religious idea. And religion does not "own" the terms or conditions that society chooses to apply to it.
You need to get this into your head.
Religions are represented by sub-cultures within a greater culture, and as such they can and do tend to create their own terms and conditions for cultural ideas like pair-bonding (as marriage between a man and a woman for the purpose of procreation, for instance). But the sub-culture is not the determinant factor for the greater culture that it exists within. So that these specifically religious terms and conditions for pair-bonding do not apply, nor do they 'override' the terms and conditions applied to pair-bonding by the culture as a whole.
You need to get this into your head.
I agree with you regarding government and marriage: that the government never had any business defining it or labeling it in the first place. And had it stayed out of it, we would not be arguing about it, now. But you are wrong when you assume that if the government had not defined pair-bonding for everyone, that religion would, could or should.
It can't, because religionists are a sub-culture within a whole culture, and therefor do not have the power nor the ability to dictate terms and conditions for pair-bonding to the whole culture.
And you need to get this into your head.
Being that you're so smart, an all, it seems you should have understood this, already.