Well, shilly-shally (or spelled as shillyshally at times) is more or less the same thing as procrastination: to keep delaying something, that must be done.
One should neither shilly-shally nor dilly-dally (another synonym for the same) anything important in life: you never know when you are going to run out of time.
The dictionary definitions for Shilly-shally are as follows:
1. The act of procrastinating; putting off or delaying or deferring an action to a later time
2. Be uncertain and vague
3. Postpone doing what one should be doing
Have a look at the video for greater clarity of the word: