Reset Mac OS X Terminal to default

Yes, there’s a command to restore all the built-in settings profiles (each item in the Settings list is called a “settings profile” or “profile”):

In the Preferences window, in the Settings panel:

1. Click the action (gear) button at the bottom of the list.
2. Choose Restore Defaults.

This will reset modified profiles and recreate any that have been deleted or renamed. Custom profiles are left as-is. (In your specific case this means that your renamed “Basic” will remain and a new “Basic” will be created.)

Correct. Just quit Terminal.app, and make a backup of the following file, then delete it.

~/Library/Preferences/com.apple.Terminal.plist

Terminal will create a new, default one once you restart it. Your preferences are stored in that preference list file – a normal Dictionary.