Definition of cryptonym in English:
 cryptonym
noun ˈkrɪptənɪmˈkriptəˌnim
A code name.
 Example sentencesExamples
-  What was your response to this revelation as to what Oswald's cryptonym was?
 -  A hundred other unseen locks and keys, oaths of secrecy, and cryptonyms stood in my way.
 -  Messages identified their recipients with a cryptonym and gave necessary instructions in coded messages.
 -  In a few cases, I was asked to not use a cryptonym or to delete the name of a case officer or the country where he had served.
 -  For many years she has been collecting materials on three topics: history of Polish Women War Service, history of underground-movement in Pomerelia 1939-1945 and history of the Department of Foreign Communications of the Home Army Main Headquarters, cryptonym ‘Zagroda’ - ‘Cottage’.
 -  One knew one's fellow students only by their cryptonyms and one did not ask them where they lived.
 -  The new project had been given an official cryptonym for use in cable traffic: Henceforth it would be known as HARDNOSE.
 
Derivatives
  
adjective krɪpˈtɒnɪməs
 Mailer comes up with a truly ingenious plot device: Harvey assigns Harry to track down the cryptonymous C.I.A. file clerk who, as Harvey sees it, defied his authority; reluctantly, Harry must trail himself.
 Example sentencesExamples
-  One unnamed, cryptonymous administration source said the report has already been optioned to Hollywood for an undisclosed sum.
 
Origin
  
Late 19th century: from crypto- 'hidden' + -onym.