in·vag·i·na·tion 
(ĭn-văj′ə-nāshən)
(ĭn-văj′ə-nāshən)n.
1. The act or process of invaginating or the condition of being invaginated.
2. An invaginated organ or part.
3. Embryology The infolding of a portion of the outer layer of a blastula in the formation of a gastrula.