the act of shiftin' back and forth while waitin' in line, leading with your right foot, then left foot, then repeat; events include: the grocery store, concert events, movies, etc.
Sally: Hey, this line for the roller coaster is so long, Charlie!
Charlie: I know. I pass the time by doing some "shiftin' suzies" as the line moves up.
Sally: Good idea Charlie! I didn't know "shiftin' suzies" could be so convenient and fun.