Roaching
Well, I certainly couldn't come up with a better name for this one. It's when you're dating someone, and all is going really well, and though you haven't yet had "the talk," you're under the impression that you are exclusive.
Then, your best friend sees them on Tinder or Hinge and you're like "Hey, WTF?" and they're like, "I thought we were both still seeing other people. Ha ha, you're so silly."
Although this term refers to the idea that if you see one roach, it means there are more (a.k.a. their partners), I think it's safe to say that people who do this are the uncommunicative roaches themselves.
[Photo via Unsplash]