Zona pellucida Meaning, Definition & Usage

  1. noun thick membrane around the mammalian ovum; can be penetrated by one sperm in the fertilization process; usually remains around the fertilized egg until it is implanted in the wall of the uterus

WordNet

Definitions
  1. . NL. (Biol.) (a) The outer transparent layer, or envelope, of the ovum. It is a more or less elastic membrane with radiating striæ, and corresponds to the cell wall of an ordinary cell. See Ovum, and Illust. of Microscope. (b) The zona radiata.

Webster 1913