Centennial is a new cross breed hop and is sometimes known as Super Cascade. It has a strong spicy/citrusy flavour and can be used in most ale styles and some wheat beers. It is best used for bittering, with Cascade used for aroma. Its typical alpha acid levels are 9.5-11.5% depending on the harvest, so you may need to adjust the amounts used in your recipe to ensure that you match the target EBU value.
Cascade and Amarillo hops can be used as a substitute if Centennial is unavailable.