Entry 1 sense Webster, 1913 Pseudonym /so͞od'-ən-ĭmˌ/ · Pseu·do·nym · IPA /ˈsu.də.nɪm/ 01 n. A fictitious name assumed for the time, as by an author; a pen name; an alias. 1. A fictitious name assumed for the time, as by an author; a pen name; an alias.