/sɛnˈtɛniəl/ noun, pl -als [count]
US : the 100th anniversary of something (such as an important event)
We're celebrating the museum's centennial [=(Brit) centenary] this summer. [=celebrating the fact that it is 100 years old]
Next year will be the centennial of the town's founding. [=the day/year 100 years after the town was officially begun]
— compare ↑bicentennial
centennial adj, always used before a noun
a centennial year/celebration
Useful english dictionary. 2012.