An elevidiot = and elevator idiot. One who tries to step into an elevator, as the door opens, before any of the passengers who are already inside have the chance to step out.
As our elevator reached our destination, the door began to open. As I was about to exit another person tried to step inside the elevator (before I could get out) almost bumping into me, causing a moment of confusion/akwardness. As I left, crossing in front of him, under my breath I sighed "you elevidiot".