How to load the illustrator cc default brushes into brush panel?

• Choose Open Brush Library.. from the Brush Panel menu
• Navigate to any Illustrator file which contains the default brushes (or any brushes you wish to load) and open that file
• The brushes will load

If you don't know where a file is that may contain the default brushes, simply create a New Document and then save it.... then use that new file to load brushes. It will have the default brushes.

It is kind of odd that there's no "reset" option for libraries in Illustrator, but there really never has been that option.

This trick works with any AI library - brushes, swatches, symbols, graphic styles, etc.