Intussusception

noun

1. Invagination, especially an infolding of one part of the intestine into another.
2. Assimilation of new substances into the existing components of living tissue.
3. A receiving within; reception of one part within another part of the same organ, or of one organ within another of the same kind; invagination; introversion; introsusception.
4. In physiology, reception of foreign matter by a living organism, and its conversion into living tissue; ingestion, digestion, and assimilation of food, including the whole process of nutrition and growth. It is the mode of interstitial growth characteristic of organic life, as distinguished from any process of accretion by which a mineral may increase in size.
5. In botany, according to the theory proposed by Nägeli, the growth of cell-walls by the intercalation of new solid particles between those already in existence. The intussusception theory is opposed to the theory of growth by apposition, which supposes that the new particles are deposited in layers on the inner side of the cell-wall.