A mentor of mine recently recommended that I read Mika Brzezinski's book Knowing Your Value. While I have found the book very helpful in terms of inspiring women to recognize what they are worth and to learn to negotiate on their own behalves to obtain it, I also thought she gave a fantastic definition of sponsorship:
... someone who is willing to use their own social capital to help pull another up the corporate ladder...Sponsorship is more than mentorship. A mentor will advise an employee, give him or her feedback, offer career strategy, and explain the company culture... Sponsors, on the other hand, will do more by using their connections and their influence to advocate for an employee.
These are exactly the attributes we have mentioned in previous posts about obtaining a sponsor: make sure the executive who will champion your change is willing to visibly demonstrate their commitment to the change, and use their connections and political clout to ensure a successful deployment across your organization.