The noun mediocrity means the quality of being average or ordinary. You can't be great at everything — in some areas, we all fall into mediocrity.
Mediocrity, pronounced "me-dee-AH-crih-tee," has Latin parts that together literally mean "halfway up the mountain." You can see how it still applies — in climbing the mountain — or ladder — of success, mediocrity is in the middle, neither leading the pack nor sprawling on ground, giving up. Such of person of this middle-level of success can also be called a mediocrity. That's a second definition of the word.