The definition of mediocre is something that is just average, or not very good.
When your dinner is edible but not very good, this is an example of when it is mediocre.
Of ordinary or undistinguished quality.
Neither very good nor very bad; ordinary; average.
Not good enough; inferior.
Origin of mediocre
From the late Middle English medioker, from the French mÃ©diocre, from the Middle French mÃ©diocre, from the Classical Latin mediocris (“in a middle state", “of middle size", “middling", “moderate", “ordinary"), from medius (“middle") + ocris (“rugged mountain"); compare mediocrely and mediocrity.