eclo·sion \-ōzhən\noun (-s) Etymology: French éclosion, from éclore to hatch, from (assumed) Vulgar Latin exclaudere to hatch out (transitive), alteration (influenced by Latin claudere to close) of Latin excludere to hatch out (transitive), exclude — more at exclude, close 1.of a full-grown insect: the act of emerging from the pupal case 2.of an insect larva: the act of hatching from the egg