Entry 1 sense Webster, 1913 Antediluvial /(ăn`tē̇*dĭ*lū"vĭ*al)/ · An·te·di·lu·vi·al · IPA /ˌantɪdɪˈluːvɪəl/ 01 a. Before the flood, or Deluge, in Noah's time. 1. Before the flood, or Deluge, in Noah's time.