medusid,n.anda.Zool.|mɪˈdjuːsɪd| [ad.mod.L. Medūsidæpl., f. Medusa: see -id.] a.n. A jelly-fish of the family Medusidæ. b.adj. Belonging to the Medusidæ. 1861J. R. Greene Man.Anim.Kingd., Cœlent. 61 The adult Medusid.Ibid. 63 Some true Medusids.Ibid. 118 A group of Medusid forms.