And did you notice that the second definition related to the word, 'marriage,' as already defined in definition one, which was very specific?
I can't address the other points in your post, as I don't believe anyone can change the definition of the word, marriage, without violating the copyright.
Do you have an objection against using a different word to describe homosexual contracts?
The point is words can and do have more than one meaning and do evolve over time. If you mentioned you were having problems with your mouse, I'd think you were talking about a computer peripheral. Thirty years ago, someone might think your rodent was ill. I don't understand your comment about copyright. Do you call your mouse a point and click peripheral since the definition of mouse is already taken?
Do you have an objection against using a different word to describe homosexual contracts?
Are you suggesting we reinstate "Separate But Equal" again? Plessy v. Ferguson might cause some problems with that. Don't you think we've learned something from past civil rights issues?
Here's what I see as a few problems with playing definitional semantics... Where does it stop? Assume we use the term civil unions. Will this be restricted to same-sex couples or can opposite-sex couples choose this option as well? What do you call the spouses in this arrangement? Can you even use the term spouse? What about the children in these relationships? Will they be sons and daughters or male/female children of a civil union? Extend this on to other relationships such as aunts, uncles, cousins, etc. Where's the stopping point? Don't you think the whole idea of using separate definitions is stigmatizing to those involved?
Can you imagine hearing a "mother of a same-sex partner in a civil union" introduce her "female child of her daughter's same-sex partner in a civil union"? Most folks won't bother with such nonsense and use traditional terms.