Narcissistic self-reference that an online contributor can use to signify that he or she has reached the hundredth-post marker of Urban Dictionary submissions.
(A compound of CENTenary (or CENTennial number) + senSATION. ;)
-- "That's it! U.D. published submission Number One Hundred of mine!" -- "You've reached your centenary on that count. Now you've become a centsation in your own mind, haven't you?"