(1):

(a.) Relating to, or associated with, the commemoration of an event that happened a hundred years before; as, a centennial ode.

(2):

(a.) Happening once in a hundred years; as, centennial jubilee; a centennial celebration.

(3):

(a.) Lasting or aged a hundred years.

(4):

(n.) The celebration of the hundredth anniversary of any event; a centenary.