Sorry for the delayed response; I've been on the road. It means that the school determined that you would probably succeed in their program but had some doubts or issues or found your profile less compelling than others'. It means that if a certain number of the people they extended offers to turn down their offers and attend another school, Chicago may offer you a place. Since Chicago is a top-choice school most of the people it offers places to will probably take them so your chances of getting in are not great.
You should accept wait-list status if you are willing to wait to find out whether Chicago will admit you. Check Chicago's letter/email to you and their website FAQs for how much new information they are open to receiving from you. To my knowledge Chicago is a program that welcomes contact from wait-listees if they do have updates or new information to provide. You could even try contacting them and asking them to give you some clue as to what is holding your application back.
Co-Author of: MBA Admission for Smarties: The No-Nonsense Guide to Acceptance at Top Business Schools
Follow Accepted on Twitter
Friend Accepted on Facebook
Subscribe to Accepted's Blog