Steve-ing is another term for third-wheeling. Based on the TikTok audio when it goes, "Just you and me, just us, and your friend Steve." If someone is being a Steve, they are thrid-wheeling a couple in a romantic relationship.
"I was hanging out with Belana and Liam, and ending up Steve-ing the entire time."
Person 1: "Dude, I feel like such a Steve right now,"
Person 2: "Why?"
Person 1: "Cause you two are making out, and I'm just sitting here!"