n. A renewal of the appearance, powers, or feelings of youth.n. In biology, a transformation whereby the entire protoplasm of a vegetative cell changes into a cell of a different character—that is, into a primordial cell which subsequently invests itself with a new cell-wall and forms the starting-point of the life of a new individual. It occurs in numerous algæ, as Œdogonium, and also in some diatoms.n. The renewal of vitality, which has been exhausted through repeated cell-division, by the sexual union of two cells into a cell of compound origin.