The word is cupronickel and it's just what it says, a combination of copper and nickel.
Cupronickel alloy is often used for coins. For example, the outer cladding of US dimes, quarters, and halves is an alloy of 25% nickel and 75% copper; British 20p coins are 84% copper and 16% nickel while 5p, 10p, and 50p coins are 75/25; Australian 5, 10, 20, and 50-cent coins are also 75/25.
Cupronickel is a copper alloy. It contains nickel, iron, and manganese. It can be used in condenser tubes and in heat exchangers.