1) Rule by those who are of average or below average competence.
2) A society in which people with little (if any) talent and skill are dominant and highly influential.
3) A social or administrative system which is like an antithesis to a meritocracy.
Eg 1) "With the presidency of George W. Bush, America has completed its transition from democracy to mediocracy."
2)"The success of Big Brother is indicative of our present society being a in a state of mediocracy."
(mediocre & -cracy), government of & responsive to mediocrity; rule by the most exceptionally average, superfluously adequate, or quintessentially ordinary citizens; government of the average, by the average, & for the average.
a comedy web series about college, careers, and the mediocre fluff in between, featuring a dopey film student, a hot latina, and a whole bunch of other misfits
"Hey Steve, did you happen to catch the last episode of Mediocracy on MediocracyTV.com? I heard it was a real knee-slapper."
The 41st through 44th presidents of the United States--George Herbert Walker Bush, William Jefferson Clinton, George W. Bush and Barack Hussein Obama--make up the mediocracy that governed the U.S. for the last part of the 20th and early 21st Centuries.