/ ˈænsestə(r); NAmE / noun
1.
a person in your family who lived a long time ago :
His ancestors had come to America from Ireland.
SYN forebear
2.
an animal that lived in the past which a modern animal has developed from :
a reptile that was the common ancestor of lizards and turtles
3.
an early form of a machine which later became more developed
SYN forerunner :
The ancestor of the modern bicycle was called a penny-farthing.
—compare descendant
► an·ces·tral / ænˈsestrəl; NAmE / adjective :
her ancestral home (= that had belonged to her ancestors )
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WORD ORIGIN
Middle English : from Old French ancestre , from Latin antecessor , from antecedere , from ante before + cedere go.