Entry 1 sense Webster, 1913 Gymnosomata /(jĭm"nō̇*sō"mȧ*tȧ [or] jĭm"nō̇*sŏm"ȧ*tȧ)/ · Gym·no·so·ma·ta · IPA 01 n. pl. One of the orders of Pteropoda. They have no shell. 1. One of the orders of Pteropoda. They have no shell.(Zool.)