You are in a nonmonogamous relationship that, when a relationship develops with another woman, qualifies as polyamorous. In that case, it would be a triad, and if the only kind of relationship you are interested in is with other women for both of you to be involved with, we usually call that unicorn hunting (the unicorn being the other woman).
As AT said, you basically have an open relationship, and you can stop there when talking about it if you don't want to get into the specifics. Is it polyamory? If a relationship develops, or if it is the goal, yes. When you do it for fun, it isn't. You can do both, as AT also said.
Either way, you are welcome to ask for advice around here if you have any problems.