verb

• (transitive) To withdraw the status of legal tender from a coin (etc.) and remove it from circulation.
  "A bill to demonetize existing French gold coinage has been introduced in the Chamber of Deputies by Deputies Lenoir, Bouffandeau, and Eymond. The purpose is to force hoarders to bring out gold estimated at 4,000,000,000 francs which is still kept in hiding in spite of patriotic appeals to the owners to exchange it for notes."
• (transitive) To declare ineligible or worthless as a medium of exchange or as legal tender.
  "1943 Post Office Department, U.S., A Description of United States Postage Stamps Issued by the Post Office Department from July 1, 1847, to April 1, 1945 [sic]. Washington: United States Government Printing Office; p4: Stamps of 1847 and 1851 Demonetized These stamps are obsolete and worthless for postage. A reasonable time after hostilities began in 1861 was given for the exchange of stamps in the hands of the public and for the replacement of post office stocks. Their acceptance in the prepayment of postage was ordered discontinued in the several States and Territories, […]"
• (Internet, transitive) To demote (published content, or its creator) so that it is no longer eligible to earn money for its publisher.
  "The site has the ability to demonetize a video."