Dictionary:

dematerialize

  (dē'mə-tîr'ē-ə-līz')

To deprive of or lose apparent physical substance; make or become immaterial: Mirrors have the effect of dematerializing a wall. The dry ice seemed to dematerialize as it sublimated.

The move from physical certificates to electronic book keeping. Actual stock certificates are slowly being removed and retired from circulation in exchange for electronic recording.

Investopedia Says:
With the age of computers and the Depository Trust Company, securities no longer need to be in certificate form. They can be registered and transferred electronically.

Related Links:
What if you've discovered some old shares in bearer form? Follow our tips and find out what they're worth. Old Stock Certificates: Lost Treasure Or Wallpaper?

The phenomenon of disappearance of phantom forms, human beings, or objects after being manifested or materialized. The terms apports and asports refer to the materialization and dematerialization of objects, involving their disappearance at one place and reappearance at another place some distance away. No satisfactory scientific theory for reported materialization or dematerialization has yet been offered, and little evidence has been produced to suggest that such phenomena in fact occur.

There are, of course, numerous anecdotal tales of materialization and dematerialization. Cases have been reported of dis-appearance and reappearance of persons, sometimes over hundreds of miles, often referred to as teleportation and transfiguration.

In the case of phantoms or spirits of the dead, the materialization is said to be formed from ectoplasm, a mysterious psychic substance exuded by a medium. Ectoplasm was often faked by mediums through the use of phosphor-covered cheesecloth and similar artifacts. Cases have also been reported of partial materialization and dematerialization by mediums such as Elizabeth d'Esperance.

The verb has one meaning:

Meaning #1: become immaterial; disappear
  Synonym: dematerialise
  Antonym: materialize (meaning #1)