Below an expected or usual level of quality.
Subpar means not very good. It's not what you want or expect.
Examples:
The movie was subpar, not very good.
Her work was subpar, not as good as usual.
The subpar cake didn't taste very good.
The subpar team lost every game.
The subpar sandwich was just bread and butter.
The subpar toy broke the first time I played with it.