Noun, pl. zygotes
1. The initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo. In single-celled organisms, the zygote divides to produce offspring, usually through meiosis. (wikipedia.org)
2. A fertilized egg cell. (wiktionary.com)
3. A cell in diploid state following fertilization or union of haploid male sex cell (e.g. sperm) and haploid female sex cell (e.g. ovum). (www.biology-online.org)
Word origin: from Greek ζυγωτός zygōtos “joined” or “yoked”, from ζυγοῦν zygoun “to join” or “to yoke”