Images from GUI Bloopers, by Jeff Johnson. Used without permission.
What's wrong with this?
Radically consistent means that each term used in the application has strictly one meaning, and each concept used in the application is represented by strictly one word.
During product design, you should develop a "product lexicon" which details each concept used in the application, and which word will represent that concept to the users. The end result of developing this conceptual model is a vocabulary which will be adhered to when developing the application and all supporting materials.
Where possible, you should use industry standard terms. Pick up the style guides which are available for the most common graphical operating environments.
You will notice that in the example above, the word "select" is used only for its industry-standard definition, to mean highlighting items by clicking. The instance of "select" on the button on the right has been replaced by "add."