nom de guerre vs pseudonym

nom de guerre and pseudonym both are nouns.

Word	Noun	Adjective	Verb	Adverb
nom de guerre	Yes	No	No	No
pseudonym	Yes	No	No	No

As nouns, nom de guerre and pseudonym are synonyms defined as:

nom de guerre and pseudonym: a fictitious name used when the person performs a particular social role

Other synonyms of nom de guerre include anonym.

nom de guerre (noun)	pseudonym (noun)
a fictitious name used when the person performs a particular social role	a fictitious name used when the person performs a particular social role