/zuy gos"i tee, zi-/ , n. Genetics.
1. the characterization of an individual's hereditary traits in terms of gene pairing in the zygote from which it developed. Cf. homozygous, heterozygous .
2. the characterization of twinning and multiple births in terms of the combination of alleles for particular hereditary traits. Cf. monozygotic, dizygotic .
[ 1945-50; ZYG- + -OSITY or ZYGOS(IS) + -ITY ]