ancestor

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person from whom one is descended, especially if more remote than a grandparent; a forebear.
• noun A forerunner or predecessor.
• noun Law The person from whom an estate has been inherited.
• noun Biology The actual or hypothetical organism or stock from which later kinds evolved.

from The Century Dictionary.

• noun One from whom a person is descended in the line of either father or mother; a forefather; a progenitor.
• noun 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.
• noun 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.

from the GNU version of the Collaborative International Dictionary of English.

• noun One from whom a person is descended, whether on the father's or mother's side, at any distance of time; a progenitor; a fore father.
• noun (Biol.) An earlier type; a progenitor.
• noun (Law) One from whom an estate has descended; -- the correlative of heir.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One from whom a person is descended, whether on the father's or mother's side, at any distance of time; a progenitor; a forefather.
• noun An earlier type; a progenitor
• noun law One from whom an estate has descended;—the correlative of heir.
• noun figuratively One who had the same role or function in former times.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun someone from whom you are descended (but usually more remote than a grandparent)