Mediocre means average, poor. It is an adjective of two genders that qualifies the one or the one that is in the mean between two terms of comparison, that is, which is neither good nor bad, which is neither small nor big etc. For example: "A mediocre book".
The expression mediocre is also used to refer to that or that which has little merit, which is ordinary, insignificant. irrelevant, vulgar.
The adjective mediocre is usually used to qualify that which is below average, which has little value, little quality, something ordinary and insignificant, but it is often used as an insult, in a pejorative sense, in order to attack verbally.
Being mediocre means not having enough qualities or skills to stand out in what you set out to do, whether in your personal or professional life. A mediocre person is vulgar, has few qualities, is an intellectually poor person.
Mediocrity is a feminine noun that names the state or quality of what is mediocre, which reveals lack of merit, vulgarity, mediocre individual, without talent.