Entry 1 sense Webster, 1913 Endosperm /ĕn'-dəs-pẽrmˌ/ · En·do·sperm · IPA /ˈɛndəspˌɜrm/ 01 n. The albumen of a seed; -- limited by recent writers to that formed within the embryo sac. 1. The albumen of a seed; -- limited by recent writers to that formed within the embryo sac.(Bot.)