When you're walking and someone is approaching from the opposite direction, you both try to pass on the same side, moving left and right simultaniously, until you have an awkward near-collision.
"This morning I was walking to class and this guy and I tibby-tabbled on the sidewalk for like 10 seconds. It was so uncomfortable... I couldn't get by him. We both laughed awkwardly."
by Katie-Paige April 19, 2009