The nearly mature ovum after the first meiotic division has been completed and the second initiated; in most higher mammals, the second meiotic division is not completed unless fertilization occurs. [G. ootidion, a diminutive egg. See -id (2)]
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oo·tid (oґo-tid) a mature oocyte; one of four cells derived from the two consecutive divisions of the primary oocyte, and corresponding to the spermatids that are derived from division of the primary spermatocyte. In mammals, the second maturation division is not completed unless fertilization occurs; hence the ootid has male as well as female pronuclear (haploid) elements.Medical dictionary. 2011.