zona pellucida

noun, plural zo·nae pel·lu·ci·dae [zoh-nee puh–loo-si-dee, pel-yoo-] /ˈzoʊ ni pəˈlu sɪˌdi, pɛlˈyu-/. Anatomy.

1. the transparent, noncellular layer surrounding the ovum of mammals, often having radial striations.

n.

1. The thick solid transparent outer membrane of a developed mammalian ovum.oolemma