I looked up "Significant other" as one phrase on dictionary.com and got this-

significant other
n.
1. A person, such as a spouse or lover, with whom one shares a long-term sexual relationship.
2. A person, such as a family member or close friend, who is important or influential in one's life: “The most important variable in successful smoking cessation is the support of significant others in the new nonsmoker's life” (Carolyn Reuben).

The first one sounds perfect, but the second sounds much less important. I don't like the second definition.

Another confusion is that Terry is a unisex name. People may wonder when you say "my significant other, Terry" or "my life partner, Terry" if you are straight or gay. Not that it's any of their buisness, and you may or may not care what they think.

My coworker is in the same boat. She is in her 40's and has a long time live in boyfriend. They share a bank account and basically live as a married couple, but are not actually married. She usually refers to him as her boyfriend, but I always think that sounds odd. One because of her age, but also because they are so much more than a boyfriend/girlfriend. When I think of a boyfriend/girlfriend I think of a couple that is dating and they past the dating point.