Co-partner, Other Significant Other (OSO), Significant Other, Partners, Lovers.....
I often refer to my boyfriend as my boyfriend when talking to others, because if they don't know he's a guy-a lot will assume he's a girl since they know I'm married and bisexual.
But-within our group, he's my OSO, other significant other.
To one another, we refer back to pet names (all of us) because the other words are only needed for communicating to someone else about our dynamic-if we so choose.
"Love As Thou Wilt"