Definition of a single parent

What makes someone a single parent?

My mom is calling me a single parent yet I’m still with my bf. He’s just away doing trucking for a while to get us caught up on bills. I don’t like it ,but I’m trying to handle myself in a mature way as possible. We aren’t married yet, but she’s calling me a single parent.

So I’m wondering from women with kids or pregnant that have partners that are away from home for work, what do you think? And your experience of dealing with your partners being away.