From Longman Dictionary of Contemporary Englishnom de plumenom de plume /ˌnɒm də ˈpluːm $ ˌnɑːm-/ noun (plural noms de plume (same pronunciation)) [countable] formal ALa name used by a writer instead of their real name SYN pen name
Examples from the Corpus
nom de plume• Jason in fact, may have been a horror-movie nom de plume.Origin nom de plume (1800-1900) French “pen name” 