The condition of being folded inward or sheathed.

synonym: introversion.

Roget 357: organized world, organized nature; living nature, animated nature; living beings; organic remains, fossils.    protoplasm, cytoplasm, protein; albumen; structure etc. 329; organization, organism.    [Science of living beings] biology; natural history, organic chemistry, anatomy, physiology; zoology etc. 368; botany; microbiology, virology, bacteriology, mycology etc. 369; naturalist.    archegenesis etc. (production) 161^†; antherozoid^†, bioplasm^†, biotaxy^†, chromosome, dysmeromorph^†; ecology, oecology; erythroblast [Physio.], gametangium^†, gamete, germinal matter, invagination [Biol.]; isogamy^†, oogamy^†; karyaster^†; macrogamete^†, microgamete^†; metabolism, anabolism, catabolism; metaplasm^†, ontogeny, ovary, ovum, oxidation, phylogeny, polymorphism, protozoa, spermary^†, spermatozoon, trophoplasm^†, vacuole, vertebration^†, zoogloea^†, zygote.    Darwinism, neo-Darwinism, Lamarkism, neoLamarkism, Weismannism.    morphology, taxonomy.    ... show more

The folding in of an outer layer so as to form a pocket in the surface:
— The invagination of the blastula.

synonyms: infolding, introversion, intussusception.

Dutch: instulping