No Good Word For Older Non-married Couples

It occurred to me that when two older people are dating (let’s say over 40) calling themselves boyfriend and girlfriend doesn’t seem like the appropriate terms.
Merriam-Webster has the following definitions:

  • Girlfriend – a woman that someone is having a romantic or sexual relationship with
  • Boyfriend – a man that someone is having a romantic or sexual relationship with.

The above definitions are rather generic and everybody uses them from the pre-teens to the grey-hair crowd. Shouldn’t there be a more mature name for the older folks?
I think when the above terms were invented it was assumed that by 30 everybody would be married or dead so we didn’t have to consider them. Then came longer life-spans, women’s liberation, free sex, etc.

 
For example, on the website http://english.stackexchange.com someone asked the following question:

“I’m in my mid 40s and dating this lady of a similar vintage. I am trying to find a good word to describe our relationship, but “girlfriend” and “boyfriend” seems inappropriate for us. It reminds me of those forty year old guys who say “I’m gittin’ down wi ma hommies.” It communicates, but it seems out of place.
Perhaps it is the “girl” and “boy” part that bothers me.
Any suggestions for something more appropriate?”

So there are other people out there besides me who are pondering this question (okay maybe I have to much time on my hand)!
If you are introducing your significant other to someone and you are over 40, what do you call them? In my case: friend? girlfriend? Lover? Partner? Mistress (Not)? significant other?
How much is too much information? If I introduce my significant other as ‘friend’ she feels as if I don’t want people to know we are dating. If I introduce her as my lover that may be too much information though this is implied with the word girlfriend also.
At the end of the day it may just depend on how serious your relationship is as each of the above terms may imply varying levels of commitment. Until someone comes up with a better term I guess I will just keep calling my significant other my ‘girl friend’.

 

What do others think?