First of all, ignore those other ignorant definitions. A zahir is a person, object, or thing that, once one has looked upon it or
considered it for but a single moment, becomes an obsession which slowly takes over a person's life completely. It can be something simple such as a coin or a mummified monkey's paw, or something intangible such as an idea. It can also be a living person or an animal. So "zahir" = something which causes an irresistable obsession in a person.
See, "The Zahir" by Phillip Jose Borges. The internet meme
smile.jpg is a kind of zahir.
For all his ideals had dwindled down to a single obsession, that only she could fulfill his one desire, for Karen had become his zahir.