Easton's Bible Dictionary
A name employed in the New Testament with reference to Abraham (Hebrews 7:4), the sons of Jacob (Acts 7:8, 9), and to David (2:29). This name is generally applied to the progenitors of families or "heads of the fathers" (Joshua 14:1) mentioned in Scripture, and they are spoken of as antediluvian (from Adam to Noah) and post-diluvian (from Noah to Jacob) patriachs. But the expression "the patriarch," by way of eminence, is applied to the twelve sons of Jacob, or to Abraham, Isaac, and Jacob.
"Patriachal longevity presents itself as one of the most striking of the facts concerning mankind which the early history of the Book of Genesis places before us...There is a large amount of consentient tradition to the effect that the life of man was originally far more prolonged than it is at present, extending to at least several hundred years. The Babylonians, Egyptians, and Chinese exaggerated these hundreds into thousands. The Greeks and Romans, with more moderation, limited human life within a thousand or eight hundred years. The Hindus still farther shortened the term. Their books taught that in the first age of the world man was free from diseases, and lived ordinarily four hundred years; in the second age the term of life was reduced from four hundred to three hundred; in the third it became two hundred; in the fourth and last it was brought down to one hundred" (Rawlinson's Historical Illustrations).
Noah Webster's New International Dictionary of the English Language
1. (n.) The father and ruler of a family; one who governs his family or descendants by paternal right; -- usually applied to heads of families in ancient history, especially in Biblical and Jewish history to those who lived before the time of Moses.
2. (n.) A dignitary superior to the order of archbishops; as, the patriarch of Constantinople, of Alexandria, or of Antioch.
3. (n.) A venerable old man; an elder. Also used figuratively.