When you put up a fence to keep your neighbor's off your property and make clear where the property line is, this is an example of when you demarcate.
When a book reviewer makes clear distinctions between light reading books he reviews and serious literature he reviews, this is an example of when he demarcates.
Origin of demarcate
- Back-formation from demarcation
From American Heritage Dictionary of the English Language, 5th Edition
- Back-formation of demarcation.