n. One from whom a person is descended in the line of either father or mother; a forefather; a progenitor.n. In law, one, whether a progenitor or a collateral relative, who has preceded another in the course of inheritance; one from whom an inheritance is derived: the correlative of heir: sometimes used specifically of the immediate progenitor.n. In biology, according to the theory of evolution, the hypothetical form or stock, of an earlier and presumably lower type, from which any organized being is inferred to have been directly or indirectly developed.