Entry 1 sense Webster, 1913 Spongoblast /(spŏṉ"gō̇*blăst)/ · Spon·go·blast · IPA 01 n. One of the cells which, in sponges, secrete the spongin, or the material of the horny fibers. 1. One of the cells which, in sponges, secrete the spongin, or the material of the horny fibers.(Zool.)