S: (n) zona pellucida (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)
S: (v) regulate, regularize, regularise, order, govern (bring into conformity with rules or principles or usage; impose regulations) "We cannot regulate the way people dress"; "This town likes to regulate"