Entry 1 sense Webster, 1913 Progenitor /prōj-ĕn'-ĭt-ẽr/ · Pro·gen·i·tor · IPA /pɹoʊˈd͡ʒɛn.ɪ.tɚ/ 01 n. An ancestor in the direct line; a forefather. 1. An ancestor in the direct line; a forefather. “And reverence thee their great progenitor.” — Milton.