estrange

To estrange people may sound like adding wobbly antennae and an extra eyeball to their faces. Really, estrange means to push apart people who were once close to each other and cause them to be like strangers.

The verb estrange comes from the Old French estranger, "to treat like a stranger.” Estrange is often used when talking about family members who are no longer in contact with each other. You can also speak about wanting to estrange the neighbor’s dog from your flowerbed or a writer who estranges her readers by using too many big words. If you're looking for a synonym that is less “strange” but more “alien,” try alienate.