How to Reset the Mac OS X Dock to Default Icon Set
The first time you login to a new user account, boot a fresh Mac, or a clean Mac OS X install, you’ll be presented with a default Dock selection without any customizations, which includes a variety of apps depending on the Mac hardware and what software is installed.
A common default Mac OS X Dock icon set would include apps like Launchpad, Safari, iTunes, Calendar, Contacts, Pages, Keynote, Numbers, Photos, iMovie, Mail, Messages, and the other pre-bundled apps the Mac comes with.
Users usually are quick to customize their Docks with their own app choices, but if you ever want to reset the Dock to the default state and start anew, you can do that at any time by using a defaults command.