Freebase(0.00 / 0 votes)Rate this definition: Fer. Fer is a red French wine grape variety that is grown primarily in South West France and is most notable for its role in the Appellation d'Origine Contrôlée wines of Gaillac, Marcillac and Béarn but can also be found as minor component in the wines of Madiran, Cabardès and Bergerac.