nom de guerre
    n 1: a fictitious name used when the person performs a
         particular social role [syn: pseudonym, anonym, nom de
         guerre]

Nom \Nom\, n. [F. See Noun.]
   Name.
   [1913 Webster]

   Nom de guerre, literally, war name; hence, a fictitious
      name, or one assumed for a time.

   Nom de plume, literally, pen name; hence, a name assumed by
      an author as his or her signature.
      [1913 Webster]