So many answers. A shift that isn't normal in that work place, starting at 10 AM instead of 8 AM. The two main answers are, second shift because it swings between first and graveyard. Or in the factories around the Midwest, swing shift means people swing back and forth between first, second and third shifts, changing every week or month to work that block of time. It's done to keep people from getting bored and to be fair to everyone so no one is stuck working one shift. It plays heck with appointments and baby sitters.
A swing shift means some weeks you work day shift and other weeks you work night shift- usually you'll work 12 hour days for say 4 days, then you get 3 days off- then you work 3, 12 hour shifts and get 4 days off. Does that make sense?