The Collaborative International Dictionary of English v.0.48:
Forefather \Fore"fa`ther\ (?; 277), n.
One who precedes another in the line of genealogy in any
degree, but usually in a remote degree; an ancestor.
Respecting your forefathers, you would have been taught
to respect yourselves. --Burke.
Forefathers' Day, the anniversary of the day (December 21)
on which the Pilgrim Fathers landed at Plymouth,
Massachusetts (1620). On account of a mistake in reckoning
the change from Old Style to New Style, it has generally
been celebrated on the 22d.