Oeuf: Egg. A recipe for oeufs farcis (stuffed eggs: remember farce?) is here: http://ile-maurice.tripod.com/oeufsfarcis.htm
Oignon piqué: French for "stabbed onion". With a clove, tack a bay leaf with onto a peeled onion. Stabbed onions are used to flavor soups and sauces.
Oignon brûlé: French for "burnt onion" (think of créme brûlé, and the burnt sugar on top). Charred half onions give color and flavor to stocks and sauces.
Oblique: this is a type of cut, with two angle-cut sides.